Thermosetting resin composition, multilayer body using same, and circuit board

ABSTRACT

Thermosetting resin compositions for manufacturing circuit boards and build-up circuit boards, and build-up boards, and multilayer bodies and circuit boards manufactured using these compositions are provided. A composition contains polyimide resin (A), phenol resin (B), and epoxy resin (C) components. The mixing ratio by weight (A)/[(B)+(C)] is 0.4 to 2.0, the ratio being the ratio of the weight of (A) to the total weight of (B) and (C). By using such a composition, multilayer bodies and circuit boards, excellent in dielectric characteristics, adhesiveness, processability, heat resistance, flowability, etc. can be manufactured. A composition contains a polyimide resin (A), a phosphazene (D), and a cyanate ester (E). D includes a phenolic hydroxyl group-containing phenoxyphosphazene (D-1) and/or a crosslinked phenoxyphosphazene (D-2) prepared by crosslinking (D-1), (D-2) having at least one phenolic hydroxyl group. By using such a composition, multilayer bodies and circuit boards with excellent properties can be manufactured.

TECHNICAL FIELD

The present invention relates to thermosetting resin compositions whichare suitably used for manufacturing circuit boards, such as flexibleprinted circuit boards (FPCs) and build-up circuit boards, and tomultilayer bodies and circuit boards manufactured using suchthermosetting resin compositions.

More particularly, the invention relates to a thermosetting resincomposition which contains a polyimide resin, a phenol resin, and anepoxy resin, and to a multilayer body and a circuit board eachmanufactured using such a thermosetting resin composition. The inventionrelates to a thermosetting resin composition which is excellent indielectric characteristics, adhesiveness, processability, heatresistance, flowability, etc., and to a multilayer body and a circuitboard each manufactured using such a thermosetting resin.

Furthermore, the invention relates to a thermosetting resin compositioncontaining a polyimide resin, a phosphazene compound, and a cyanateester compound, and to a multilayer body and a circuit board eachmanufactured using such a thermosetting resin composition. The inventionrelates to a thermosetting resin composition which is excellent indielectric characteristics, processability, heat resistance, flameretardance, etc., and to a multilayer body and a circuit board eachmanufactured using such a thermosetting resin composition.

BACKGROUND ART

Recently, in order to improve information processing capability inelectronic devices, frequencies of electrical signals transmittedthrough circuits on wiring boards have been increased. Consequently,even if the frequencies of electrical signals are increased, it isdesired to maintain electrical reliability of wiring (circuit) boardsand to prevent decreases in the transmission speed of electrical signalsand loss of electrical signals in the circuits.

Meanwhile, the circuit boards are usually provided with protective filmsfor protecting the wiring boards and circuits, and insulating layers,such as interlayer insulating films for ensuring insulation between theindividual layers in multilayer wiring boards. Since the protectivefilms and the insulating layers, such as interlayer insulating films,are disposed on the wiring boards, they are required to haveadhesiveness so that they are bonded to the wiring boards, in additionto insulating properties. In particular, when multilayer wiring boardsare manufactured by laminating flexible printed circuit boards (FPCs),build-up circuit boards, or the like, the individual boards are bondedand fixed to each other by the interlayer insulating films. Therefore,the interlayer insulating films are required to have excellent adhesionto the boards or the like. Accordingly, the protective films and theinsulating layers, such as interlayer insulating films, are formed usingadhesive materials having adhesiveness.

Consequently, in order to improve information processing capability inelectronic devices by increasing the frequencies of electrical signals,even if insulating layers are formed using adhesive materials, it isdesirable to obtain high reliability of wiring boards in the GHz(gigahertz) range and to avoid adverse effects on the transmission ofelectrical signals.

In the past, as the adhesive material for wiring boards, for example, anepoxy adhesive material or a thermoplastic polyimide adhesive materialhas been used. The epoxy adhesive material has excellent processability,such as capability of bonding adherends under low-temperature andlow-pressure conditions, and also has excellent adhesiveness toadherends. The thermoplastic polyimide adhesive material has excellentheat resistance, such as low thermal expansion and high thermaldecomposition temperature.

Furthermore, Japanese Unexamined Patent Application Publication No.8-27430 (Publication Date: Jan. 30, 1996 (Heisei 8)) describes that useof a film adhesive prepared by mixing a polyimide resin having a glasstransition temperature in a predetermined range, an epoxy compound, anda compound having an active hydrogen group reactive with the epoxycompound enables low-temperature, short-time bonding between adherendsand achieves heat resistance reliability at high temperatures.

However, an epoxy resin obtained by curing the epoxy adhesive materialhas a dielectric constant of 4 or more and a dielectric loss tangent of0.02 or more in the GHz range, resulting in a problem that satisfactorydielectric characteristics cannot be obtained.

Furthermore, with respect to an adhesive material using a polyimideresin obtained by curing the thermoplastic polyimide adhesive material,in order to allow adherends to adhere to each other using such amaterial, the adherends must be bonded to each other underhigh-temperature and high-pressure conditions, causing a problem inprocessability.

Furthermore, the film adhesive described in Japanese Unexamined PatentApplication Publication No. 8-27430 can be processed at low temperaturesfor a short period of time and has excellent heat resistance reliabilityat high temperatures. However, the publication does not describedielectric characteristics. The epoxy compound contained in the filmadhesive described in Japanese Unexamined Patent Application PublicationNo. 8-27430 decreases the softening temperature of the film adhesive toimprove low-temperature processability. However, if a large amount ofthe epoxy compound is incorporated, the dielectric constant and thedielectric loss tangent are increased, resulting in a degradation indielectric characteristics.

Therefore, in order to improve information processing capability inelectronic devices by increasing the frequencies of electrical signals,it is desired to develop an adhesive material which is excellent inadhesiveness, processability, and heat resistance and which is capableof forming insulating layers having excellent dielectriccharacteristics, i.e., exhibiting a low dielectric constant and a lowdielectric loss tangent, even in the GHz range.

However, so far, with respect to resin compositions containing epoxycompounds and thermoplastic polyimide resins, there has not beenprovided a thermosetting resin composition which can be suitably usedfor manufacturing circuit boards, such as flexible printed circuitboards and build-up circuit boards, which is excellent in flowability,adhesiveness, processability, and heat resistance, and which hasexcellent dielectric characteristics in the GHz range.

Furthermore, recently, in view of environmental concerns, with respectto various materials used for electronic devices, there has been a needto take recycling into consideration and to avoid the use ofenvironmentally unfriendly substances as much as possible. For example,with respect to flame retardants, non-halogen (halogen-free) flameretardants are desired, and with respect to solders, solders that do notcontain lead (lead-free solders) are desired.

In particular, with respect to solders, in the past, eutectic solderscontaining lead have been mainly used as materials for physically andelectrically connecting wiring boards and mounted parts. However, inview of environmental concerns, the lead-free solders that do notcontain lead have come into common use. The lead free solders havemelting points that are about 40° C. higher than those of conventionalsolders containing lead. Therefore, with respect to materials for wiringboards, there has been a strong demand for further improvement in heatresistance.

As resin materials used for wiring boards, in particular, adhesivematerials and insulating materials used for the insulating layers, suchas interlayer insulating films, and the protective films, curable resincompositions including polyimide resins and cyanate ester compounds areknown as described above. However, such curable resin compositions haveproblems with respect to dielectric characteristics and processability.In order to overcome the problems in the epoxy adhesive materials andthe thermoplastic polyimide adhesive materials, as a different systemfrom that of resin compositions containing epoxy compounds andthermoplastic polyimides, Japanese Unexamined Patent ApplicationPublication No. 2001-200157 (Publication Date: Jul. 24, 2001 (Heisei13)) discloses a thermosetting resin composition containing a polyimideresin and a cyanate ester compound as an adhesive material (resinmaterial) having excellent dielectric characteristics andprocessability.

Furthermore, Japanese Unexamined Patent Application Publication No.8-8501 (Publication Date: Jan. 12, 1996 (Heisei 8)) discloses a lowdielectric constant multilayer printed circuit board which contains acyanate ester compound as a main component and which has flameretardance. Furthermore, Japanese Unexamined Patent ApplicationPublication No. 9-132710 (Publication Date: May 20, 1997 (Heisei 9))discloses a polyimide resin composition having excellent adhesiveness.

However, these conventional techniques, in particular, in theapplication of manufacturing wiring boards that meet the requirement ofimproving information processing capability in electronic devices, havedifficulty in improving various physical properties of resin materialsin a well-balanced manner. More specifically, with respect to theconventional techniques, in the resin materials used in theabove-described application, it is difficult to satisfy the requirementsof both flame retardance and other physical properties, such as heatresistance, processability (including solvent solubility), anddielectric characteristics.

For example, in the thermosetting resin composition disclosed inJapanese Unexamined Patent Application Publication No. 2001-200157, apolyimide resin is mixed with a cyanate ester compound, and thisthermosetting resin composition is effective in satisfying therequirements of dielectric characteristics, heat resistance, andprocessability. However, there is no description in the publication offlame retardance, which is an important property of the materialconstituting circuit boards. Therefore, it is not clear if thethermosetting resin composition has sufficient flame retardance.

The low dielectric constant multilayer printed circuit board disclosedin Japanese Unexamined Patent Application Publication No. 8-8501 iscomposed of a material prepared by mixing a cyanate ester compound andbrominated bisphenol A. Because of the use of the brominated phenol, themultilayer printed circuit board has flame retardance that is sufficientfor use in a wiring board. Furthermore, the polyimide resin compositiondisclosed in Japanese Unexamined Patent Application Publication No.8-8501 includes a halogen atom or a halogen-containing hydrocarbongroup. That is, in spite of the fact that recently flame-retardantmaterials that do not include halogen compounds have been stronglydesired in view of environmental concerns, a halogen compound is used.

Accordingly, so far, there has not been provided a thermosetting resincomposition in which it is possible to sufficiently satisfy therequirements of both flame retardance and other physical properties,such as dielectric characteristics, heat resistance, and processability(including solvent solubility), in view of environmental concerns, andin particular, which can be suitably used in manufacturing wiring boardsthat satisfactorily meet the requirement of improving informationprocessing capability in electronic devices.

DISCLOSURE OF INVENTION

In order to overcome the problems described above, the present inventorshave found that by using a thermosetting resin composition containing apolyimide resin, a phenol resin, and an epoxy resin as essentialcomponents, the epoxy resin and the phenol resin being mixed at apredetermined ratio with the polyimide resin, it is possible to obtain athermosetting resin composition which is excellent in flowabilityrequired for embedding a circuit, adhesiveness to an adherend, such as acircuit board, processability and handleability enabling bonding at lowtemperatures, and heat resistance with respect to thermal expansion andthermal decomposition, and which is capable of being cured to produce acured resin having excellent dielectric characteristics, i.e.,exhibiting a low dielectric constant and a low dielectric loss tangent,in the GHz range.

That is, in order to overcome the problems described above, athermosetting resin composition of the present invention contains atleast a polyimide resin component (A) containing at least one polyimideresin, a phenol resin component (B) containing at least one phenolresin, and an epoxy resin component (C) containing at least one epoxyresin. The mixing ratio by weight (A)/[(B)+(C)] is in a range of 0.4 to2.0, the mixing ratio by weight being the ratio of the weight of thepolyimide resin component (A) to the total weight of the phenol resincomponent (B) and the epoxy resin component (C).

Preferably, the mixing ratio by mole (B)/(C) is in a range of 0.4 to1.2, the mixing ratio by mole being the ratio of the number of moles ofthe hydroxyl group of the phenol resin contained in the phenol resincomponent (B) to the number of moles of the epoxy group of the epoxyresin contained in the epoxy resin component (C).

In accordance with the constituent features described above, a curedresin obtained by curing the thermosetting resin composition exhibits alow dielectric constant and a low dielectric loss tangent even in theGHz range, and thus excellent dielectric characteristics can beachieved. Specifically, with respect to a cured resin obtained byheating the thermosetting resin composition in a temperature range of150° C. to 250° C. for 1 to 5 hours, the dielectric constant can be setat 3.3 or less and the dielectric loss tangent can be set at 0.020 orless in a frequency range of 1 to 10 GHz. If the dielectric constant is3.3 or less and the dielectric loss tangent is 0.020 or less in the GHzrange, when the thermosetting resin composition of the present inventionis used as a protective material or an interlayer insulating material ofa circuit board, electrical reliability of the circuit board is ensured,and it is possible to prevent decreases in the transmission speed ofsignals and loss of signals in the circuit on the circuit board.

Furthermore, the thermosetting resin composition of the presentinvention has excellent flowability required for embedding a circuit,excellent heat resistance, such as low thermal expansion coefficient andhigh thermal decomposition temperature, excellent adhesiveness betweenthe thermosetting resin composition and an adherend, such as a conductoror a circuit board, and excellent processability during bonding betweenthe thermosetting resin composition and a conductor or a circuit board.Consequently, the thermosetting resin composition can be suitably usedfor manufacturing circuit boards, such as flexible printed circuitboards and build-up circuit boards.

As described above, the thermosetting resin composition of the presentinvention has the properties in a well-balanced manner. Therefore, thethermosetting resin composition can be suitably used for manufacturingcircuit boards and can impart good properties to circuit boards obtainedusing the thermosetting resin composition of the present invention.

Preferably, the at least one polyimide resin contained in the polyimideresin component (A) is produced by reacting an acid dianhydridecomponent containing at least one acid dianhydride represented bygeneral formula (1):

(wherein V represents a divalent group selected from the groupconsisting of —O—, —CO—, —O-T-O—, and —COO-T-OCO—, T representing adivalent organic group) with a diamine component containing at least onediamine.

Preferably, the phenol resin component (B) contains at least one phenolresin selected from the group consisting of compounds having structuresrepresented by the formulae:

(wherein a, b, c, d, and e each represent an integer of 1 to 10).

Preferably, the epoxy resin component (C) contains at least one epoxyresin selected from the group consisting of compounds having structuresrepresented by the formulae:

(wherein g, h, i, j, and k each represent an integer of 1 to 10).

Thereby, it is possible to impart excellent properties, such asdielectric characteristics, flowability, heat resistance, adhesiveness,and processability, in a well-balanced manner, to the thermosettingresin composition or a cured resin obtained by curing the thermosettingresin composition.

Furthermore, in order to overcome the problems described above, amultilayer body of the present invention includes at least one resinlayer formed of the thermosetting resin composition described abovecontaining the polyimide resin, the phenol resin, and the epoxy resin asessential components, the epoxy resin and the phenol resin being mixedat a predetermined ratio with the polyimide resin.

Furthermore, in order to overcome the problems described above, acircuit board of the present invention includes the thermosetting resincomposition described above.

The multilayer body and the circuit board each include the thermosettingresin composition. Therefore, it is possible to impart, in awell-balanced manner, various properties, such as dielectriccharacteristics, flowability, heat resistance, adhesiveness, andprocessability, to the resin layers formed of the thermosetting resincomposition in the multilayer body and the circuit board. Consequently,the multilayer body and the circuit board can be manufacturedadvantageously. In particular, when the multilayer body and the circuitboard are each provided with circuits or the like, electricalreliability of the individual circuits is ensured, and it is possible toprevent decreases in the transmission speed of signals and loss ofsignals in the individual circuits.

The present inventors have also found that by selecting a combination ofa polyimide resin, a specific phosphazene compound, and a cyanate estercompound serving as components of a thermosetting resin composition, itis possible to enhance a balance between flame retardance and otherphysical properties.

That is, a thermosetting resin composition of the present inventioncontains at least a polyimide resin (A) containing at least onepolyimide resin, a phosphazene compound (D) containing at least onephosphazene compound, and a cyanate ester compound (E) containing atleast one cyanate ester compound. The phosphazene compound (D) includesa phenolic hydroxyl group-containing phenoxyphosphazene compound (D-1)and/or a crosslinked phenoxyphosphazene compound (D-2) prepared bycrosslinking the phenoxyphosphazene compound (D-1), the crosslinkedphenoxyphosphazene compound (D-2) having at least one phenolic hydroxylgroup.

In the thermosetting resin composition, preferably, the mixing ratio byweight (B)/[(A)+(D)+(E)] is in a range of 0.01 to 0.4, the mixing ratioby weight being the ratio of the weight of the phosphazene compound (D)to the total weight of the polyimide resin (A), the phosphazene compound(D), and the cyanate ester compound (E).

Furthermore, in the thermosetting resin composition, preferably, thephenoxyphosphazene compound (D-1) includes at least a cyclicphenoxyphosphazene compound (D-11) represented by general formula (2):

(wherein m represents an integer of 3 to 25; R¹ and R² each represent aphenyl group or a hydroxyphenyl group; and at least one hydroxyphenylgroup is contained per molecule) and/or a linear phenoxyphosphazenecompound (D-12) represented by general formula (3):

(wherein n represents an integer of 3 to 10,000; R³ and R⁴ eachrepresent a phenyl group or a hydroxyphenyl group; at least onehydroxyphenyl group is contained per molecule; R⁵ represents—N═P(OC₆H₅)₃, —N═P(OC₆H₅)₂(OC₆H₄OH), —N═P(OC₆H₅)(OC₆H₄OH)₂,—N═P(OC₆H₄OH)₃, —N═P(O)OC₆H₅, or —N═P(O)(OC₆H₄OH); and R⁶ represents—P(OC₆H₅)₄, —P(OC₆H₅)₃(OC₆H₄OH), —P(OC₆H₅)₂(OC₆H₄OH)₂,—P(OC₆H₅)(OC₆H₄OH)₃, —P(OC₆H₄OH)₄, —P(O)(OC₆H₅)₂, —P(O)(OC₆H₅)(OC₆H₄OH),or —P(O)(OC₆H₄OH)₂).

Furthermore, in the thermosetting resin composition, preferably, thecrosslinked phenoxyphosphazene compound (D-2) is prepared bycrosslinking the phenoxyphosphazene compound with a phenylene-basedcrosslinking group containing at least any one of an o-phenylene group,an m-phenylene group, a p-phenylene group, and a bisphenylene grouprepresented by general formula (4):

(wherein R⁷ represents —C(CH₃)₂—, —SO₂—, —S—, or —O—; and p represents 0or 1).

More preferably, the crosslinked phenoxyphosphazene compound is aphenylene-based crosslinked phenoxyphosphazene compound (D-21) having atleast one phenolic hydroxyl group, in which the cyclicphenoxyphosphazene compound (D-11) and/or the linear phenoxyphosphazenecompound (D-12) are used as the phenoxyphosphazene compound, and thephenylene-based crosslinking group lies between two oxygen atoms of thephenoxyphosphazene compound (D-1), the phenyl group and thehydroxyphenyl group being separated from the oxygen atoms, and thecontent of the phenyl group and the hydroxyphenyl group in thecrosslinked phenoxyphosphazene compound is in a range of 50% to 99.9%based on the total number of phenyl groups and hydroxyphenyl groupscontained in the phenoxyphosphazene compound.

In the thermosetting resin composition, preferably, the polyimide resin(A) contains a soluble polyimide resin.

Furthermore, in the thermosetting resin composition, preferably, thepolyimide resin (A) dissolves in an amount of 1% by weight or more in atleast one organic solvent selected from the group consisting ofdioxolane, dioxane, tetrahydrofuran, N,N-dimethylformamide,N,N-dimethylacetamide, and N-methyl-2-pyrrolidone in a temperature rangeof 15° C. to 100° C.

Furthermore, in the thermosetting resin composition, preferably, thepolyimide resin (A) contains at least one component for impartingorganic solvent solubility which is selected from the group consistingof an aliphatic compound component, an alicyclic compound component, anda bisphenol compound-alkylene oxide adduct component, so as to exhibitsolubility in a mixed solvent containing a low-boiling organic solvent.

Furthermore, in the thermosetting resin composition, preferably, thepolyimide resin (A) is produced by reacting an acid dianhydridecomponent with a diamine component or an isocyanate component, and theacid dianhydride component contains at least an acid dianhydriderepresented by general formula (1):

(wherein V represents a direct bond, —O—, —O-T-O—, —O—CO-T-CO—O—,—(C═O)—, —C(CF₃)₂—, or —C(CH₃)₂—, T representing a divalent organicgroup).

Alternatively, preferably, the polyimide resin (A) is produced byreacting an acid dianhydride component with a diamine component or anisocyanate component, and the diamine component or the isocyanatecomponent contains at least any one of a siloxane diamine, a diaminecontaining a hydroxyl group and/or a carboxyl group, a diamine havingamino groups at the meta positions, a diamine having amino groups at theortho positions, an isocyanate having an amino group at the metaposition, and an isocyanate having an amino group (isocyanato group) atthe ortho position.

In the thermosetting resin composition, preferably, the cyanate estercompound (E) includes at least one compound selected from the groupconsisting of compounds represented by the group of general formulae(1):

(wherein r represents 0 to 4).

Furthermore, in order to overcome the problems described above, amultilayer body of the present invention includes at least one resinlayer formed of the thermosetting resin composition described abovecontaining the polyimide resin (A), at least one of thephenoxyphosphazene compound (D-1) and the crosslinked phenoxyphosphazenecompound (D2), and the cyanate ester compound (E).

Furthermore, in order to overcome the problems described above, acircuit board of the present invention includes the thermosetting resincomposition described above.

The multilayer body and the circuit board each include the thermosettingresin composition. Therefore, it is possible to impart excellent heatresistance, dielectric characteristics, and flame retardance to theresin layers formed of the thermosetting resin composition in themultilayer body and the circuit board. Since the thermosetting resincomposition enables bonding at a lower temperature compared with theconventional thermoplastic polyimide resin-based adhesive material,excellent processability is also imparted to the resin layers. Moreover,since the cyanate ester compound is used, various properties, such asprocessability, heat resistance, and dielectric characteristics, arebetter balanced compared with the conventional polyimide/epoxy resinmixed adhesives. Furthermore, since the hydroxyl group-containingphosphazene compound is used, the hydroxyl group can react with theester group of the cyanate ester compound. Thereby, the structure of thephosphazene compound can be incorporated into the network structure ofthe cured resin, thus improving flame retardance without impairing heatresistance. Consequently, the thermosetting resin composition of thepresent invention enables bonding at lower temperatures compared withconventional compositions, is excellent in processability andhandleability, and is capable of exhibiting excellent heat resistance,dielectric characteristics, and flame retardance.

As a result, for example, when the thermosetting resin composition ofthe present invention is formed into a varnish solution or the like, itis possible to produce a resin preparation useful as an adhesive, acoating material, an ink, or the like. Furthermore, when thethermosetting resin composition of the present invention is formed intoresin sheets or resin films, the resin sheets or the resin films can besuitably used as multilayer bodies, such as circuit boards, e.g.,flexible printed circuit boards (FPCs) and build-up circuit boards, andlaminating materials constituting such multilayer bodies.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below. It is tobe understood that the present invention is not limited thereto.

A thermosetting resin composition of the present invention can be usedfor circuit boards, such as flexible printed circuit boards and build-upcircuit boards. The thermosetting resin composition can be used as aprotecting material for protecting the circuit boards or circuitspatterned on the circuit boards, or an interlayer insulating materialfor ensuring insulation between the individual layers in multilayercircuit boards.

First Embodiment

A thermosetting resin composition according to a first embodiment of thepresent invention contains, as essential components, a polyimide resincomponent (A) containing at least one polyimide resin, a phenol resincomponent (B) containing at least one phenol resin, and an epoxy resincomponent (C) containing at least one epoxy resin. With respect to themixing ratio of the individual components in the thermosetting resincomposition, in the mixing ratio by weight (A)/[(B)+(C)], i.e., theratio of the weight of the polyimide resin component (A) to the totalweight of the phenol resin component (B) and the epoxy resin component(C), the lower limit is preferably 0.4 or more, and more preferably 0.5or more. Furthermore, in the mixing ratio by weight (A)/[(B)+(C)], theupper limit is preferably 2.0 or less, and more preferably 1.5 or less.

If the mixing ratio by weight becomes less than 0.4, i.e., if thecontent of the phenol resin component (B) and the epoxy resin component(C) in the thermosetting resin composition becomes relatively largerthan the content of the polyimide resin component (A), in a resin sheetbefore curing, flowability increases and minimum complex viscositydecreases. Furthermore, in a resin sheet after curing, although heatresistance, which is represented by modulus of elasticity, coefficientof linear expansion, and the like, at high temperatures increases, itbecomes difficult to achieve a low dielectric constant and a lowdielectric loss tangent (hereinafter referred to as excellent dielectriccharacteristics) in the GHz (gigahertz) range.

On the other hand, if the mixing ratio by weight exceeds 2.0, i.e., ifthe content of the polyimide resin component (A) in the thermosettingresin composition becomes relatively larger than the content of thephenol resin component (B) and the epoxy resin component (C), althoughexcellent dielectric characteristics can be exhibited in the cured resinin the GHz range, adhesiveness between the thermosetting resincomposition and a conductor or a circuit board, and processabilityduring bonding between the thermosetting resin composition and aconductor or a circuit board are degraded.

In the thermosetting resin composition of the present invention, bysetting the mixing ratio by weight in the range described above, a curedresin obtained by curing the thermosetting resin composition exhibitsexcellent dielectric characteristics even in the GHz range. That is,with respect to the dielectric characteristics of a cured resin obtainedby heating the thermosetting resin composition at a temperature of 150°C. to 250° C. for 1 to 5 hours, the dielectric constant is 3.3 or lessand the dielectric loss tangent is 0.020 or less at a frequency of 1 to10 GHz. If the dielectric constant and the dielectric loss tangent arein the ranges described above, when the thermosetting resin compositionof the present invention is used as a protective material or aninterlayer insulating material in a circuit board, it is possible toensure electrical insulation of the circuit board and to preventdecreases in the transmission speed of signals and loss of signals inthe circuit on the circuit board. Therefore, a highly reliable circuitboard can be provided.

Furthermore, in the thermosetting resin composition of the presentinvention, with respect to the mixing ratio by mole (B)/(C), i.e., theratio of the number of moles of the hydroxyl group of the phenol resincontained in the phenol resin component (B) to the number of moles ofthe epoxy group of the epoxy resin contained in the epoxy resincomponent (C), the lower limit is preferably 0.4 or more, and morepreferably 0.7 or more. Furthermore, the upper limit of the mixing ratioby mole (B)/(C) is preferably 1.2 or less, and more preferably 1.1 orless.

If the mixing ratio by mole (B)/(C) becomes less than 0.4 or exceeds1.2, the dielectric characteristics of a cured resin obtained by curingthe thermosetting resin composition are adversely affected. Furthermore,the glass transition temperature, the thermal expansion coefficient, andthe modulus of elasticity at high temperatures of the thermosettingresin composition are decreased, and the heat resistance is alsodegraded.

Additionally, the number of moles of the epoxy group and the number ofmoles of the hydroxyl group are respectively calculated from the epoxyvalue and the hydroxyl value.

As described above, in the thermosetting resin composition, by settingthe compounding ratio of the polyimide resin (A), the phenol resin (B),and the epoxy resin (C) in a specific range, it is possible to obtain athermosetting resin composition which is excellent, in a well-balancedmanner, in flowability required for embedding a circuit, adhesiveness toan adherend, such as a circuit board or a conductor, processability andhandleability enabling bonding at low temperatures, heat resistance withrespect to thermal expansion and thermal decomposition, resistance tohumidity test using a pressure cooker (PCT), resistance to solderingheat, insulating properties, and dielectric characteristics of a curedresin obtained by curing the thermosetting resin composition.

The polyimide resin component (A), the phenol resin component (B), theepoxy resin component (C), and other components (F) contained in thethermosetting resin composition will be described in detail below.

(A) Polyimide Resin Component

In the thermosetting resin composition of the present invention,incorporation of a polyimide resin component (A) containing at least onepolyimide resin imparts heat resistance to the thermosetting resincomposition, imparts flexibility, excellent mechanical characteristics,and chemical resistance to a cured resin obtained by curing thethermosetting resin composition, and also imparts excellent dielectriccharacteristics, i.e., a low dielectric constant and a low dielectricloss tangent in the GHz range, to the cured resin.

The polyimide resin is not particularly limited, but is preferably asoluble polyimide resin that dissolves in an organic solvent. Herein,the term “soluble polyimide resin” means a polyimide resin thatdissolves in an amount of 1% by weight or more in an organic solvent ina temperature range of 15° C. to 100° C.

Examples of the organic solvent which may be used include at least onesolvent selected from ether solvents, such as dioxane, dioxolane, andtetrahydrofuran; acetamide solvents, such as N,N-dimethylformamide andN,N-diethylacetamide; formamide solvents, such as N,N-diethylformamide;N,N-dimethylacetamide; and pyrrolidone solvents, such asN-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone.

By using the soluble polyimide resin, when the thermosetting resincomposition of the present invention is thermally cured,high-temperature, long-time processing is not required, and the phenolresin component (B) and the epoxy resin component (C), which will bedescribed below, can be cured efficiently. Furthermore, when the solublepolyimide is used as the polyimide resin (A) in the thermosetting resinaccording to the second embodiment, which will be described below, thecyanate ester compound (E) can be cured efficiently. Consequently, useof a soluble polyimide resin as the polyimide resin is preferable inview of processability.

The polyimide resin (A) is a resin whose backbone contains an imide ringas a repeating unit. Specifically, examples of the polyimide resin (A)include polyimides (resins containing imide rings only, i.e., polyimideresins in a narrow sense) and polyimide resins in a broad sense havingrepeating units other than imide rings, such as polyamideimides,polyesterimides, polyetherimides, and maleimides.

As will be described below, the polyimide resin (A) is generallyproduced by any of the following two methods. In a first method, an aciddianhydride component and a diamine component are used as startingmonomer components, these monomer components are reacted and polymerizedto form polyamic acid, and the polyamic acid is imidized to produce apolyimide resin. In a second method, an acid dianhydride component andan isocyanate component are used as starting monomer components, andthese monomer components are reacted to produce a polyimide resin.

The specific structure of the polyimide resin (A) is not particularlylimited. In the present invention, by using an acid dianhydride and adiamine or an isocyanate each having a specific structure describedbelow as the monomer components, it is possible to produce a polyimideresin (A) that is more suitable for the thermosetting resin compositionof the present invention. Additionally, a method for producing thepolyimide resin (A) will be described later.

<Acid Dianhydride Component>

In the present invention, any acid dianhydride component can be used asa starting material for the polyimide resin (A) without limitation aslong as the acid dianhydride is capable of producing a polyimide resinthat has solubility in various types of organic solvent, heatresistance, and compatibility with the phenol resin component (B), theepoxy resin component (C), and the cyanate ester compound (E) if used asthe polyimide resin (A) in the second embodiment, which will bedescribed below. Preferably, the acid dianhydride component is anaromatic tetracarboxylic dianhydride. Specifically, the acid dianhydridecomponent preferably contains at least an acid dianhydride (for theconvenience of description, referred to as an “aromatic tetracarboxylicdianhydride”) represented by general formula (1):

(wherein V represents a direct bond, —O—, —O-T-O—, —O—CO-T-CO—O—,—(C═O)—, —C(CF3)2- , or —C(CH3)2- , T representing a divalent organicgroup).

If the aromatic tetracarboxylic dianhydride represented by generalformula (1) is used, the resulting polyimide resin (A) can have improvedsolubility in an organic solvent, improved heat resistance, and improvedcompatibility with the phenol resin component, the epoxy resincomponent, and the cyanate ester compound (E), if used for thethermosetting resin in the second embodiment which will be describedbelow.

Among the aromatic tetracarboxylic dianhydrides represented by generalformula (1), more preferred for use is an acid dianhydride (for the sakeof description, referred to as a “phenylene-based aromatictetracarboxylic dianhydride”) in which T in general formula (1)represents any of divalent organic groups (organic groups having one ortwo benzene rings) selected from the following group (2):

and divalent organic groups represented by general formula (7):

(wherein Z represents —CQH2Q-, —C(═O)—, —SO2- , —O—, or —S—, Qrepresenting an integer of 1 to 5). These phenylene-based aromatictetracarboxylic dianhydrides may be used alone or two or more of thesemay be combined appropriately. By using such an acid dianhydride, in theresulting polyimide resin (A) and thermosetting resin composition,excellent dielectric characteristics (a low dielectric constant and alow dielectric loss tangent in the GHz range) and excellent heatresistance can be exhibited.

Furthermore, among the phenylene-based aromatic tetracarboxylicdianhydrides, use of 4,4′-(4,4′-isopropylidenediphenoxy)bisphthalicdianhydride represented by the following formula:

is particularly preferable. By using this acid dianhydride, in theresulting polyimide resin (A) and thermosetting resin composition,various properties, such as solvent solubility, heat resistance,compatibility with the cyanate ester compound component, compatibilitywith the cyanate ester compound (E) if used in the second embodiment ofthe thermosetting resin, which will be described below, and dielectriccharacteristics can be better balanced. Furthermore,4,4′-(4,4′-isopropylidenediphenoxy)bisphthalic dianhydride is easilyavailable, which is advantageous.

The acid dianhydride component used in the present invention preferablycontains at least an aromatic tetracarboxylic dianhydride represented bygeneral formula (1). Furthermore, by specifying the content of the aciddianhydride represented by general formula (1) in the total aciddianhydrides, it is possible to produce a polyimide resin (A) havingexcellent physical properties.

Specifically, the aromatic tetracarboxylic dianhydride is preferablyused in an amount of 50 mole percent or more based on 100 mole percentof the total acid dianhydride component used as the starting material.Thereby, in the resulting polyimide resin (A), excellent solventsolubility, excellent compatibility with the epoxy resin, the cyanateester compound, etc., and excellent dielectric characteristics can beexhibited.

The acid dianhydride component can contain only one of the aciddianhydrides represented by general formula (1) or two or more of thesein combination in any ratio. Moreover, the acid dianhydride componentmay contain an acid dianhydride having a structure other than thestructure represented by general formula (1)(hereinafter referred to as“the other acid dianhydride”).

Specific examples of the other acid dianhydride which may be used in thepresent invention include, but are not limited to, anhydrides ofpyromellitic acid, 1,2,3,4-benzenetetracarboxylic acid,1,2,3,4-cyclobutanetetracarboxylic acid,1,2,4,5-cyclopantanetetracarboxylic acid,1,2,4,5-cyclohexanetetracarboxylic acid,3,3′,4,4′-bicyclohexyltetracarboxylic acid,2,3,5-tricarboxycyclopentylacetic acid,3,4-dicarboxy-1,2,3,4-tetrahydronaphthalene-1-succinic acid,bis(3,4-dicarboxyphenyl)methane, bis(2,3-dicarboxyphenyl)methane,1,1-bis(2,3-dicarboxyphenyl)ethane,3,3′,4,4′-diphenylsulfonetetracarboxylic acid,2,3,3′4′-diphenylsulfonetetracarboxylic acid,2,3,6,7-naphthalenetetracarboxylic acid,1,4,5,8-naphthalenetetracarboxylic acid,1,2,5,6-naphthalenetetracarboxylic acid, 3,4,9,10-tetracarboxyperyleneacid, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanoic acid,2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropanoic acid,3,3′,4,4′-dimethyldiphenylsilanetetracarboxylic acid,1,2,3,4-furantetracarboxylic acid,4,4′-bis(3,4-dicarboxyphenoxy)diphenylpropanoic acid,4,4′-hexafluoroisopropylidenediphthalic acid, and p-phenylenediphthalicacid, and lower alkyl esters thereof.

These compounds may be used alone or in appropriate combination of twoor more. As described above, it is extremely preferable to use at leastone acid dianhydride represented by general formula (1).

Among the compounds described above, particularly preferred for use areanhydrides of 2,3,3′,4′-biphenyl ether tetracarboxylic acid,2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane,4,4′-(4,4′-isopropylidenediphenoxy)bisphthalic acid,2,2′-bis(4-hydroxyphenyl)propanedibenzoate-3,3′,4,4′-tetracarboxylicacid,1,2-bis(4-hydroxyphenyl)ethylenedibenzoate-3,3′,4,4′-tetracarboxylicacid, 2,3,3′,4′-biphenyltetracarboxylic acid, or lower alkyl estersthereof. Thereby, in the resulting polyimide resin (A), solventsolubility and heat resistance can be better balanced. Among thesecompounds, the aromatic tetracarboxylic dianhydride is preferable, andthe phenylene-based aromatic tetracarboxylic dianhydride (e.g.,4,4′-(4,4′-isopropylidenediphenoxy)bisphthalic acid) is more preferable.

<Diamine Component>

With respect to the polyimide resin (A) suitably used in the presentinvention, among the starting materials, the diamine component is notparticularly limited. The diamine component used in the presentinvention is preferably a diamine capable of producing the polyimideresin (A) in which excellent solubility in various types of organicsolvent, heat resistance, resistance to soldering heat, PCT resistance,low water absorption, and thermoplasticity are exhibited. Examples ofsuch a diamine component include a diamine containing an aromaticstructure, such as a benzene ring (phenyl group).

Specifically, the diamine component preferably contains a diamine (forthe convenience of description, referred to as an “aromatic diamine”)represented by general formula (8):

(wherein each Y independently represents —C(═O)—, —SO2- , —O—, —S—,—(CH2)m- , —NHCO—, —C(CH3)2- , —C(CF3)2- , —C(═O)O—, or a direct bond;each R represents a hydrogen atom, a halogen atom, or an alkyl grouphaving 1 to 4 carbon atoms; and m and r each independently represent aninteger of 1 to 5). By using such an aromatic diamine, in the resultingpolyimide resin (A), excellent solubility and heat resistance and lowwater absorption can be exhibited. Additionally, a plurality of Ys,which are repeating units in general formula (8), may be the same ordifferent.

Examples of the aromatic diamine represented by general formula (8)include, but are not limited to, bis[4-(3-aminophenoxy)phenyl]methane,bis[4-(4-aminophenoxy)phenyl]methane,1,1-bis[4-(3-aminophenoxy)phenyl]ethane,1,1-bis[4-(4-aminophenoxy)phenyl]ethane,1,2-bis[4-(3-aminophenoxy)phenyl]ethane,1,2-bis[4-(4-aminophenoxy)phenyl]ethane,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(3-aminophenoxy)phenyl]butane,2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,1,3-bis(3-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene,1,4′-bis(4-aminophenoxy)benzene, 4,4′-bis(4-aminophenoxy)biphenyl,bis[4-(3-aminophenoxy)phenyl]ketone,bis[4-(4-aminophenoxy)phenyl]ketone,bis[4-(3-aminophenoxy)phenyl]sulfide,bis[4-(4-aminophenoxy)phenyl]sulphide,bis[4-(2-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]sulfone,bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether,1,4-bis[4-(3-aminophenoxy)benzoyl]benzene,1,3-bis[4-(3-aminophenoxy)benzoyl]benzene,4,4′-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether,4,4′-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether,4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone,4,4′-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone,bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone,1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene,1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene,4,4′-diaminodibenzyl sulfoxide, bis(4-aminophenoxy)phenylphosphineoxide, bis(4-aminophenoxy)-N-phenylamine, and2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. These diamines maybe used alone or in appropriate combination of two or more.

Among the aromatic diamines represented by general formula (8), from thestandpoint of improving solubility in various types of solvent, anaromatic diamine having amino groups at the meta positions or the orthopositions is preferable. In particular, a diamine represented by generalformula (9):

(wherein each Y independently represents —C(═O)—, —SO₂—, —O—, —S—,—(CH₂)_(m)—, —NHCO—, —C(CH₃)₂—, —C(CF₃)₂—, —C(═O)O—, or a direct bond;each R represents a hydrogen atom, a halogen atom, or an alkyl grouphaving 1 to 4 carbon atoms; and m and r each independently represent aninteger of 1 to 5), i.e., an aromatic diamine having amino groups at themeta positions (for the convenience of description, referred to as a“meta-aromatic diamine”), is more preferable. If such an aromaticdiamine is used, the resulting polyimide resin (A) can have moreexcellent solubility compared with the case in which an aromatic diaminehaving amino groups at the para positions is used.

Examples of the aromatic diamine represented by general formula (8)include 1,1-bis[4-(3-aminophenoxy)phenyl]ethane,1,2-bis[4-(3-aminophenoxy)phenyl]ethane,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(3-aminophenoxy)phenyl]butane,2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane,1,3-bis(3-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene,bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl] sulfone,bis[4-(3-aminophenoxy)phenyl] ether,1,4-bis[4-(3-aminophenoxy)benzoyl]benzene,1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, and4,4′-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether.

Among the aromatic diamines described above, use of1,3-bis(3-aminophenoxy)benzene is particularly preferable. By using thisaromatic diamine, in the resulting polyimide resin (A) and thermosettingresin composition, physical properties, such as solubility in varioustypes of solvent, resistance to soldering heat, and PCT resistance, canbe further improved.

Furthermore, in the present invention, as the diamine component, adiamine having a hydroxyl group and/or a carboxyl group is alsopreferably used. If the diamine having a hydroxyl group and/or acarboxyl group is used, at least one of the hydroxyl group and thecarboxyl group is introduced into the resulting polyimide resin (A). Thehydroxyl group and the carboxyl group can promote the curing of thethermosetting component.

Therefore, in the polyimide resin (A) prepared using the diamine havingthe hydroxyl group and/or carboxyl group, it is possible to cure thephenol resin (B) and the epoxy resin (C), which are thermosettingcomponents, or the cyanate ester compound (E) when used as the polyimideresin (A) in the second embodiment, at low temperatures or in a shortperiod of time. Furthermore, since the cyanate ester compound isreactable with the hydroxyl group and/or the carboxyl group,crosslinking through the epoxy resin is enabled in the resultingpolyimide resin (A). Consequently, it is possible to impart moreexcellent heat resistance, resistance to soldering heat, and PCTresistance to the resulting thermosetting resin composition.

The diamine having the hydroxyl group and/or the carboxyl group is notparticularly limited as long as the diamine includes at least one of thehydroxyl group and the carboxyl group. Specific examples thereof includediaminophenols, such as 2,4-diaminophenol; hydroxybiphenyl compounds,such as 3,3′-diamino-4,4′-dihydroxybiphenyl,4,4′-diamino-3,3′-dihydroxybiphenyl,4,4′-diamino-2,2′-dihydroxybiphenyl, and4,4′-diamino-2,2′,5,5′-tetrahydroxybiphenyl; hydroxydiphenylalkanes,such as 3,3′-diamino-4,4′-dihydroxydiphenylmethane,4,4′-diamino-3,3′-dihydroxydiphenylmethane,4,4′-diamino-2,2′-dihydroxydiphenylmethane,2,2-bis[3-amino-4-hydroxyphenyl]propane,2,2-bis[4-amino-3-hydroxyphenyl]propane,2,2-bis[3-amino-4-hydroxyphenyl]hexafluoropropane, and4,4′-diamino-2,2′,5,5′-tetrahydroxydiphenylmethane; hydroxydiphenylether compounds, such as 3,3′-diamino-4,4′-dihydroxydiphenyl ether,4,4′-diamino-3,3′-dihydroxydiphenyl ether,4,4′-diamino-2,2′-dihydroxydiphenyl ether, and4,4′-diamino-2,2′,5,5′-tetrahydroxydiphenyl ether; diphenyl sulfonecompounds, such as 3,3′-diamino-4,4′-dihydroxydiphenyl sulfone,4,4′-diamino-3,3′-dihydroxydiphenyl sulfone,4,4′-diamino-2,2′-dihydroxydiphenyl sulfone, and4,4′-diamino-2,2′,5,5′-tetrahydroxydiphenyl sulfone;bis[(hydroxyphenoxy)phenyl]alkane compounds, such as2,2-bis[4-(4-amino-3-hydroxyphenoxy)phenyl]propane;bis(hydroxyphenoxy)biphenyl compounds, such as4,4′-bis(4-amino-3-hydroxyphenoxy)biphenyl;bis[(hydroxyphenoxy)phenyl]sulfone compounds, such as2,2-bis[4-(4-amino-3-hydroxyphenoxy)phenyl] sulfone; diaminobenzoicacids, such as 3,5-diaminobenzoic acid; carboxybiphenyl compounds, suchas 3,3′-diamino-4,4′-dicarboxybiphenyl,4,4′-diamino-3,3′-dicarboxybiphenyl,4,4′-diamino-2,2′-dicarboxybiphenyl, and4,4′-diamino-2,2′,5,5′-tetracarboxybiphenyl; carboxydiphenylalkanes,such as 3,3′-diamino-4,4′-dicarboxydiphenylmethane,4,4′-diamino-3,3′-dicarboxydiphenylmethane,4,4′-diamino-2,2′-dicarboxydiphenylmethane,2,2-bis[4-amino-3-carboxyphenyl]propane,2,2-bis[3-amino-4-carboxyphenyl]hexafluoropropane, and4,4′-diamino-2,2′,5,5′-tetracarboxydiphenylmethane; carboxydiphenylether compounds, such as 3,3′-diamino-4,4′-dicarboxydiphenyl ether,4,4′-diamino-3,3′-dicarboxydiphenyl ether,4,4′-diamino-2,2′-dicarboxydiphenyl ether, and4,4′-diamino-2,2′,5,5′-tetracarboxydiphenyl ether; diphenyl sulfonecompounds, such as 3,3′-diamino-4,4′-dicarboxydiphenyl sulfone,4,4′-diamino-3,3′-dicarboxydiphenyl sulfone,4,4′-diamino-2,2′-dicarboxydiphenyl sulfone, and4,4′-diamino-2,2′,5,5′-tetracarboxydiphenyl sulfone;bis[(carboxyphenoxy)phenyl]alkane compounds, such as2,2-bis[4-(4-amino-3-carboxyphenoxy)phenyl]propane;bis(hydroxyphenyl)alkanes, such as2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane;bis(hydroxyphenoxy)biphenyl compounds, such as4,4′-bis(4-amino-3-hydroxyphenoxy)biphenyl; andbis[(carboxyphenoxy)phenyl]sulfone compounds, such as2,2-bis[4-(4-amino-3-carboxyphenoxy)phenyl] sulfone.

Among the diamines having the hydroxyl group and/or the carboxyl groupdescribed above, use of 3,3′-dihydroxy-4,4′-diaminobiphenyl representedby the following formula:

is particularly preferable so that satisfactory resistance to solderingheat and PCT resistance are obtained.

When the polyimide resin (A) is synthesized, as the diamine component,preferably, at least one aromatic diamine represented by general formula(8) and/or at least one diamine having the hydroxyl group and/orcarboxyl group are used. More preferably, both diamines are used.Furthermore, when the 3,3′-dihydroxy-4,4′-diaminobiphenyl describedabove is used as the diamine having the hydroxyl group and/or carboxylgroup, it is possible to impart excellent resistance to soldering heatand resistance to humidity test using a pressure cooker (PCT) to theresulting thermosetting resin composition.

In the present invention, as the diamine component, in addition to thearomatic diamine and/or the diamine having the hydroxyl group and/or thecarboxyl group, other diamine may be used. Herein, the other diamine canbe appropriately selected depending on the application and requiredphysical properties of the target polyimide resin (A) or thethermosetting resin composition, and the other diamine is notparticularly limited to specific compounds.

Examples of the other diamine include, but are not limited to,3,3′-diamino ether, m-phenylenediamine, o-phenylenediamine,p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine,bis(3-aminophenyl) sulfide, (3-aminophenyl)(4-aminophenyl) sulfide,bis(4-aminophenyl) sulfide, bis(3-aminophenyl) sulfoxide,(3-aminophenyl)(4-aminophenyl) sulfoxide, bis(3-aminophenyl) sulfone,(3-aminophenyl)(4-aminophenyl) sulfone, bis(4-aminophenyl) sulfone,3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone,3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane,4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether,3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,bis[4-(3-aminophenoxy)phenyl]sulfoxide, bis[4-(aminophenoxy)phenyl]sulfoxide, 4,4′-diaminodiphenylmethane,3,3′-dimethyl-4,4′-diaminodiphenylmethane,3,3′,5,5′-tetramethyl-4,4′-diaminodiphenylmethane,3,3′,5,5′-tetraethyl-4,4′-diaminodiphenylmethane,3,3′-dimethyl-5,5′-diethyl-4,4′-diaminodiphenylmethane,4,4′-methylenebis(cyclohexylamine),3,3′-dimethyl-4,4′-diaminodicyclohexylmethane,3,3′-dimethoxy-4,4′-diaminodiphenylmethane,3,3′-diethoxy-4,4′-diaminodiphenylmethane, bis(3-aminophenyl) ether,bis(4-aminophenyl) ether, 3,3′-diethyl-4,4′-diaminodiphenyl ether,3,3′-dimethoxy-4,4′-diaminodiphenyl ether,3,3′-dimethyl-4,4′-diaminodiphenyl sulfone,3,3′-diethyl-4,4′-diaminodiphenyl sulfone,3,3′-dimethoxy-4,4′-diaminodiphenyl sulfone,3,3′-diethoxy-4,4′-diaminodiphenyl sulfone,3,3′-dimethyl-4,4′-diaminodiphenylpropane,3,3′-diethyl-4,4′-diaminodiphenylpropane,3,3′-dimethoxy-4,4′-diaminodiphenylpropane,3,3′-diethoxy-4,4′-diaminodiphenylpropane,1,3-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane,4,4′-diaminodiphenyl sulfide, 3,3′-dimethyl-4,4′-diaminodiphenylsulfide, 3,3′-diethyl-4,4′-diaminodiphenyl sulfide,3,3′-dimethoxy-4,4′-diaminodiphenyl sulfide,3,3′-diethoxy-4,4′-diaminodiphenyl sulfide, 2,2′-diaminodiethyl sulfide,2,4′-diaminodiphenyl sulfide, 1,2-bis(4-aminophenyl)ethane,1,1-bis(4-aminophenyl)ethane, o-toluidine sulfone,bis(4-aminophenyl)diethylsilane, bis(4-aminophenyl)ethylphosphine oxide,bis(4-aminophenyl)-N-methylamine, 1,2-diaminonaphthalene,1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,6-diaminonaphthalene,1,7-diaminonaphthalene, 1,8-diaminonaphthalene, 2,3-diaminonaphthalene,2,6-diaminonaphthalene, 1,4-diamino-2-methylnaphthalene,1,5-diamino-2-methylnaphthalene, 1,3-diamino-2-phenylnaphthalene,9,9-bis(4-aminophenyl)fluorene, 4,4′-diaminobiphenyl,3,3′-diaminobiphenyl, 3,3′-dichloro-4,4′-diaminobiphenyl,3,3′-dimethyl-4,4′-diaminobiphenyl, 3,4′-dimethyl-4,4′-diaminobiphenyl,3,3′-dimethoxy-4,4′-diaminobiphenyl, 2,4-diaminotoluene,2,5-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminotoluene,1,3-diamino-2,5-dichlorobenzene, 1,4-diamino-2,5-dichlorobenzene,1-methoxy-2,4-diaminobenzene, 1,3-diamino-4,6-dimethylbenzene,1,4-diamino-2,5-dimethylbenzene, 1,4-diamino-2-methoxy-5-methylbenzene,1,4-diamino-2,3,5,6-tetramethylbenzene,1,4-bis(2-methoxy-4-aminopentyl)benzene,1,4-bis(1,1-dimethyl-5-aminopentyl)benzene, o-xylenediamine,m-xylenediamine, p-xylenediamine, 9,10-bis(4-aminophenyl)anthracene,3,3′-diaminobenzophenone, 2,6-diaminopyridine, 3,5-diaminopyridine,1,3-diaminoadamantane, 3,3′-diamino-1,1,1′-diadamantane,N-(3-aminophenyl)-4-aminobenzamide, 4,4′-diaminobenzanilide,4-aminophenyl-3-aminobenzoate, 2,2-bis(4-aminophenyl)hexafluoropropane,2,2-bis(3-aminophenyl)hexafluoropropane,2-(3-aminophenyl)-2-(4-aminophenyl)hexafluoropropane,2,2-bis[4-(2-chloro-4-aminophenoxy)phenyl]hexafluoropropane,1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane,1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane,1,3-bis(3-aminophenyl)hexafluoropropane,1,3-bis(3-aminophenyl)decafluoropropane,2,2-bis(3-amino-4-methylphenyl)hexafluoropropane,2,2-bis(5-amino-4-methylphenyl)hexafluoropropane, and1,4-bis(3-aminophenyl)but-1-en-3-yne. These compounds may be used aloneor two or more of these may be combined appropriately.

Additionally, among the other diamines described above (or the diamineshaving the hydroxyl group and/or the carboxyl group) used in the presentinvention, depending on the application, a diamine containing a siloxanebond (—Si—O—) (for the convenience of description, referred to as a“siloxane diamine”) may be preferably used.

Examples of the siloxane diamine include a compound represented bygeneral formula (10):

(wherein each R⁹ represents an alkyl group having 1 to 12 carbon atomsor a phenyl group; each y represents an integer of 1 to 40; and zrepresents an integer of 1 to 20). If such a siloxane diamine is used,in the resulting polyimide resin (A), solubility in organic solvents canbe improved.

Furthermore, besides the siloxane diamine, examples of the other diaminewhich may be preferably used in the present invention include isophoronediamine, hexamethylenediamine, and diaminodicyclohexylmethane. If any ofthese diamines is used, in the resulting polyimide resin (A), solubilityin organic solvents and heat resistance can be further improved.

The diamine component used in the present invention preferably containsat least the diamine represented by general formula (8), andparticularly preferably further contains the diamine having the hydroxylgroup and/or the carboxyl group. By specifying the contents of theindividual diamines in the total diamine component, it is possible toproduce a polyimide resin (A) having excellent physical properties.

Specifically, preferably, the diamine represented by general formula (8)is used in an amount of 60 to 90 mole percent and the diamine having thehydroxyl group and/or the carboxyl group is used in an amount of 1 to 40mole percent based on 100 mole percent of the total diamine componentused as the starting material. If the contents of the individualdiamines are in the ranges described above, it is possible to avoid thesituation in which the solubility, resistance to soldering head, and PCTresistance of the resulting polyimide resin (A) are impaired.

Furthermore, although the content of the other diamine in the totaldiamine component is not particularly limited, the other diamine ispreferably used in an amount of less than 10 mole percent based on 100mole percent of the total diamine component used as the startingmaterial.

<Isocyanate Component>

As described above, the polyimide resin (A) used in the presentinvention may be produced by reacting an acid dianhydride component witha diamine component or an isocyanate component. Consequently, in thepresent invention, instead of the diamine component, an isocyanatecomponent can be used as a starting material.

As the isocyanate component used in the present invention, anyisocyanate can be used as long as the isocyanate is capable of producingthe polyimide resin (A) in which excellent solubility in various typesof organic solvent, heat resistance, resistance to soldering heat, PCTresistance, low water absorption, and thermoplasticity are exhibited.Specific examples of the isocyanate include diusocyanates correspondingto the diamines described above.

More specifically, examples of the isocyanate include, but are notlimited to, diisocyanates corresponding to the aromatic diaminesrepresented by general formula (8) and the aromatic diamines havingamino groups at the meta positions or the ortho positions [e.g., adiisocyanate corresponding to 1,3-bis(3-aminophenoxy)benzene];diisocyanates corresponding to diamines having the hydroxyl group and/orthe carboxyl group [e.g., a diisocyanate corresponding to3,3′-dihydroxy-4,4′-diaminobiphenyl]; diisocyanates corresponding tosiloxane diamines; and diisocyanates corresponding to isophoronediamine, hexamethylenediamine, diaminodicyclohexylmethane, and the like.These compounds may be used alone or in combination of two or more.

<Structure that can be Introduced Other than Imide Ring>

Examples of the polyimide resin (A) used in the present inventioninclude both polyimide resins in a narrow sense and polyimide resins ina broad sense having repeating units other than imide rings, such aspolyamideimides, polyesterimides, and polyetherimides. In this way, astructure other than the imide ring may be introduced into the polyimideresin (A).

A polyamideimide can be synthesized using trimellitic anhydride as anacid dianhydride component and an aromatic group-containing diamine orisocyanate as a diamine component or isocyanate component.

Next, a polyesterimide can be synthesized using trimellitic anhydride asan acid dianhydride component and the diamine component described above.Specifically, first, by reaction of trimellitic anhydride with thediamine component, an imide ring-containing dicarboxylic acidrepresented by general formula (11):

(wherein R¹⁰ represents a divalent organic group) is synthesized.Subsequently, the dicarboxylic acid is reacted with the other aciddianhydride which will be described below and a diol, anddehydrocondensation is carried out. A polyesterimide is therebyproduced.

Next, a polyetherimide is produced using an ether bond-containingcompound as at least one of the acid dianhydride component and thediamine component.

Herein, the trimellitic anhydride used as the acid dianhydride componentin the polyamideimide or the polyesterimide can be copolymerized withother acid dianhydride. Examples of the other acid dianhydride include,but are not limited to, aliphatic or alicyclic dicarboxylic acids, suchas oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid,azelaic acid, dodecanedioic acid, cyclohexanedicarboxylic acid, maleicacid, maleic anhydride, itaconic acid, itaconic anhydride, dimer acids,and hydrogenated dimer acids; aromatic dicarboxylic acids, such asterephthalic acid, isophthalic acid, naphthalenedicarboxylic acid,diphenylmethane-4,4-dicarboxylic acid, diphenylether-4,4-dicarboxylicacid, bis[(4-carboxy)phthalimide]-4,4-diphenyl ether,bis[(4-carboxy)phthalimide]-a,a′-metaxylene, and 5-hydroxyisophthalicacid; tricarboxylic acids, such as butane-1,2,4-tricarboxylic acid andnaphthalene-1,2,4-tricarboxylic acid, and dianhydrides thereof; andtetracarboxylic acids, such as pyromellitic acid,benzophenonetetracarboxylic acid, benzene-1,2,3,4-tetracarboxylic acid,biphenyltetracarboxylic acid, naphthalenetetracarboxylic acid,perylene-3,4,9,10-tetracarboxylic acid, ethylene glycolbis(anhydrotrimellitate), propylene glycol bis(anhydrotrimellitate), and3,3′,4′-oxydiphthalic acid, and dianhydrides thereof. These compound maybe used alone or two or more of these may be combined appropriately.

Moreover, in order to further improve solubility in an organic solventwith respect to the resulting polyimide resin (A), for example, analiphatic compound component, an alicyclic compound component, analkylene oxide adduct of a bisphenol compound, or the like may beintroduced into the polyimide resin (A).

Among these, with respect to the aliphatic compound component and thealicyclic compound component, if an aliphatic or alicyclic compound isselected as the acid dianhydride component, the diamine component, orthe isocyanate component, it is possible to introduce the aliphaticcompound component or the alicyclic compound component into the backboneof the polyimide resin (A). Specific examples of the aliphatic oralicyclic compound include, but are not limited to, dimer acids,hydrogenated dimer acids, isophorone diamine, hexamethylenediamine,diaminodicyclohexylmethane, and isocyanates corresponding thereto.

Furthermore, examples of the alkylene oxide adduct of the bisphenolcompound include ethylene oxide adducts and propylene oxide adducts ofbisphenol A, bisphenol F, bisphenol S, and biphenols. In thesecompounds, the amount of the alkylene oxide to be added is notparticularly limited. However, from the standpoint of the thermalstability of the resulting polyimide resin (A), the amount of thealkylene oxide to be added to one end is 5 moles or less, preferably 3moles or less, and more preferably 2 moles or less, on an average.

When the aliphatic compound component, the alicyclic compound component,or the alkylene oxide adduct of the bisphenol compound is introducedinto the polyimide resin (A), this component tends to have a high effectof improving solubility and a low effect of decreasing heat resistance.Consequently, when this component is introduced, the amount ofintroduction is set in a range of 1 to 100 mole percent based on thetotal amount of the acid dianhydride component or the total amount ofthe diamine component or the isocyanate component. Thereby, in theresulting polyimide resin (A), solubility in organic solvents, inparticular, aromatic, ketone, or ether solvents, can be improved.

<Synthesis of Polyimide Resin (A)>

The polyimide resin (A) used in the present invention can be produced bya known method. Specifically, depending on the starting materials used,the synthesis methods (production methods) of the polyimide resin (A)can be broadly divided into the following two methods.

In a first method, as starting materials (monomer components), an aciddianhydride component and a diamine component are used. These monomercomponents are subjected to polycondensation to synthesize a polyamicacid, which is a precursor, and the polyamic acid is chemically orthermally cyclodehydrated (imidized). Thus, the first method isperformed in two stages. On the other hand, in a second method, asstarting materials, an acid dianhydride component and an isocyanatecomponent are used. These monomer components are polymerized to producea polyimide resin. Thus, the second method is a one-stage method.

Synthesis (production) of a polyamic acid and imidization of thepolyamic acid in the first method and the second method will bedescribed in detail in that order below.

<Synthesis (Production) Process for Polyamic Acid in First Method>

In the synthesis (production) process for polyamic acid, an aciddianhydride component containing at least one acid dianhydride and adiamine component containing at least one diamine are reacted with eachother in an organic solvent. In this process, substantially equimolaramounts of the acid dianhydride componentiand the diamine component arereacted with each other. Consequently, when only one acid dianhydrideand one diamine are used, these are mixed in equimolar amounts. When twoor more acid dianhydrides and two or more diamines are used, the totalamount of the acid dianhydride component (total amount of a plurality ofacid dianhydrides) and the total amount of the diamine component (totalamount of a plurality of diamines) are adjusted to be equimolar. When aplurality of acid dianhydrides and diamines are used, a polyamic acidcopolymer can be prepared in any manner.

In the synthesis of the polyamic acid, the method for reacting theindividual monomer components are not particularly limited. In general,a method is used in which substantially equimolar amounts of the aciddianhydride component and the diamine component are dissolved in anorganic solvent, and then stirring is performed under controlledreaction conditions until polymerization is completed. By this method,it is possible to prepare a solution in which the polyamic acid isdissolved in the organic solvent (hereinafter referred to as a “polyamicacid solution”).

With respect to the order of addition of the acid dianhydride componentand the diamine component, examples of the method include, but are notlimited to, (1) a method in which a diamine component is dissolved in anorganic solvent, and then an acid dianhydride component is addedthereto; (2) a method in which an acid dianhydride component isdissolved in an organic solvent, and then a diamine component is addedthereto; and (3) a method in which an adequate amount of a diaminecomponent is added and dissolved in an organic solvent, an aciddianhydride component is added thereto in excess of the diaminecomponent, and then the diamine component is added in an amountcorresponding to the excess amount of the added acid dianhydridecomponent. Herein, the term “dissolved” means not only a state in whicha solvent completely dissolves a solute but also a state in which asolute is uniformly dispersed or diffused in a solvent and which issubstantially the same as the dissolved state.

In the synthesis reaction of the polyamic acid, synthesis conditions arenot particularly limited as long as the conditions allow the monomercomponents to be polymerized to synthesize a polyamic acidsatisfactorily. In the present invention, among the synthesisconditions, the temperature conditions, the reaction time, and theorganic solvent used are preferably defined as follows:

The temperature range for the synthesis reaction of the polyamic acid isnot particularly limited as long as the acid dianhydride component andthe diamine component can be polymerized. The upper limit is preferably80° C. or less, more preferably 50° C. or less, and still morepreferably 30° C. or less, and particularly preferably 20° C. or less.The lower limit is not particularly limited, but is preferably higherthan or equal to the temperature that allows the reaction to proceed andprevents the precipitation of the polymer produced by the reaction.Specifically, although depending on the starting materials used for thepolymerization, the lower limit is preferably −20° C. or more, andparticularly preferably 0° C. or more.

Furthermore, the reaction time in the synthesis reaction for thepolyamic acid is not particularly limited as long as the time allows thepolymerization reaction between the acid dianhydride component and thediamine component to be completed. The upper limit is generallysufficient at 50 hours and may be 12 hours or less. On the other hand,the lower limit is preferably 30 minutes or more, and more preferably 3hours or more.

In the synthesis reaction of the polyamic acid, any organic solventcapable of dissolving the polyamic acid sufficiently can be used withoutlimitation. Usually, a polar organic solvent is used. Furthermore, fromthe standpoints that an increase in viscosity is prevented to facilitatestirring during the synthesis of the polyamic acid and that theresulting polyimide resin (A) is easily dried, and the like, preferably,a polar organic solvent that can dissolve the polyamic acidsatisfactorily and that has a boiling point as low as possible isselected. Thereby, the production process of the polyimide resin (A) canbe performed more efficiently.

Examples of the polar organic solvent which may be used in the synthesisreaction of the polyamic acid include, but are not limited to, sulfoxidesolvents, such as N,N-dimethyl sulfoxide and diethyl sulfoxide;formamide solvents, such as N,N-dimethylformamide andN,N-diethylformamide; acetamide solvents, such as N,N-dimethylacetamideand N,N-diethylacetamide; pyrrolidone solvents, such asN-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; phenol solvents, suchas phenol, o-cresol, m-cresol, p-cresol, xylenol, halogenated phenol,and catechol; hexamethylphosphamide; and γ-butyrolactone.

These polar organic solvents may be used alone or two or more of thesemay be combined appropriately. Furthermore, as necessary, any of thepolar organic solvents and an aromatic hydrocarbon, such as xylene ortoluene, may be combined for use.

Specific conditions of the polyamic acid solution obtained by thesynthesis method described above are not particularly limited. Thelogarithmic viscosity number is preferably set in the following range.That is, in a 100 ml of N-methyl-2-pyrrolidone solution containing 0.5 gof polyamic acid, the logarithmic viscosity number at 30° C. ispreferably in a range of 0.2 to 4.0 dl/g, and more preferably in a rangeof 0.3 to 2.0 dl/g.

<Imidization of Polyamic Acid in First Method>

The polyimide resin (A) used in the present invention is produced byimidization of the polyamic acid obtained by the synthesis methoddescribed above. The specific method of imidization is not particularlylimited. For example, the polyamic acid in the polyamic acid solution iscyclodehydrated by a thermal method or a chemical method. Herein, theterm “thermal method” means a method in which a polyamic acid solutionis dehydrated by heat treatment, and the term “chemical method” means amethod in which dehydration is performed using a dehydrating agent.Other than these methods, a method in which imidization is carried outby heat treatment under reduced pressure may be used.

(1) Thermal Method

The thermal method is not particularly limited as long as the polyamicacid is cyclodehydrated by heating. For example, in a specific method,imidization is allowed to proceed by heat treatment of the polyamic acidsolution and at the same time the solvent is evaporated, etc. The heattreatment conditions are not particularly limited. Preferably, theheating temperature is 300° C. or less and the heating time is in arange of about 5 minutes to 10 hours. Furthermore, a thermal cyclizationprocess by means of reflux of toluene, xylene, or the like may also beused. By such a thermal method, a polyimide resin (A) can be obtained.

(2) Chemical Method

With respect to the chemical method, for example, in a method, by addingstoichiometric amounts or more of a dehydrating agent and a catalyst tothe polyamic acid solution, dehydration reaction and evaporation of thesolvent are performed. By such a chemical method, a polyimide resin (A)can be obtained.

Specific examples of the dehydrating agent include aliphatic acidanhydrides, such as acetic anhydride; aromatic acid anhydrides, such asbenzoic anhydride; and carbodiimides, such asN,N′-dicyclohexylcarbodiimide and N,N′-diisopropylcarbodiimide.Furthermore, specific examples of the catalyst include aliphatictertiary amines, such as triethylamine; aromatic tertiary amines, suchas dimethylaniline; and heterocyclic tertiary amines, such as pyridine,α-picoline, β-picoline, γ-picoline, and isoquinoline.

The conditions for the chemical method are not particularly limited.Preferably, the reaction temperature is 100° C. or less, and thereaction time is in a range of about one minute to 50 hours. Althoughthe conditions for the evaporation of the organic solvent are also notparticularly limited, the heating temperature is preferably 200° C. orless, and the heating time is in a range of about 5 minutes to 12 hours.

(3) Heating Treatment under Reduced Pressure

One of the methods other than the thermal method and the chemical methodis a method (for the convenience of description, referred to as a“reduced-pressure heating method”) in which imidization is carried outby heat treatment under reduced pressure. By the reduced-pressureheating method, it is also possible to produce the polyimide resin (A).The treatment conditions in the reduced-pressure heating method are notparticularly limited as long as imidization is allowed to take place.Among the treatment conditions, the heating conditions and the pressureconditions are preferably set as described below.

First, with respect to the heating conditions, the heating temperatureis set in a range of 80° C. to 400° C. In order to perform imidizationand dehydration efficiently, the lower limit is set preferably at 100°C. or more, and more preferably at 120° C. or more. On the other hand,the maximum temperature (upper limit) in the heating treatment ispreferably set to be lower than the thermal decomposition temperature ofthe resulting polyimide resin (A). Consequently, the upper limit of theheating temperature is preferably set in a range of about 180° C. to350° C., which usually corresponds to the completion temperature forimidization.

Next, the pressure conditions are not particularly limited as long asthe pressure is low. Specifically, the pressure is preferably in a rangeof 0.001 to 0.9 atm, more preferably in a range of 0.001 to 0.8 atm, andmost preferably in a range of 0.001 to 0.7 atm. In other words, theupper limit of the pressure in the reduced-pressure heating method isless than 1 atm, preferably 0.9 atm or less, more preferably 0.8 atm orless, and most preferably 0.7 atm or less. On the other hand, the lowerlimit is 0.001 atm or more, although not limited thereto.

In the process in which the polyamic acid is imidized by thereduced-pressure heating method, water generated during imidization canbe actively removed out of the system. Therefore, it is possible toinhibit hydrolysis of the polyamic acid. Furthermore, the aciddianhydride component, which is a starting material of the polyamicacid, contains compounds having an open-circular form at one end orcompounds having an open-circular form at both ends, these compoundsbeing impurities. By employing the reduced-pressure heating method, itis possible to cyclize the compounds having an open-circular form at oneend or the compounds having an open-circular form at both ends. As aresult, the molecular weight of the resulting polyimide resin (A) can befurther increased.

(4) Solidification Method in which Solvent is not Evaporated

In the thermal method, the chemical method, or the reduced-pressureheating method described above, the solvent is evaporated in theimidization process. However, a thermal method or a chemical method inwhich the solvent is not evaporated and a solid polyimide resin (A) isobtained is also available. Specifically, in this method, the solutionof the polyimide resin (A) prepared by the thermal method or thechemical method is added to a poor solvent to precipitate the polyimideresin, and drying is performed. Thereby, a solid polyimide resin (A) isobtained.

As the poor solvent, any solvent that mixes satisfactorily with asolvent of the solution of the resulting polyimide resin (A) but doesnot easily dissolve the polyimide resin (A) can be used withoutlimitation in this method. Specific examples thereof include acetone,methanol, ethanol, isopropanol, benzene, Methyl Cellosolve (registeredtrademark), methyl ethyl ketone, and water.

In this method, since the polyimide resin (A) is precipitated in thepoor solvent, the solid polyimide resin (A) is obtained, and it is alsopossible to perform purification by removing impurities. Examples of theimpurities include unreacted monomer components (acid dianhydrides anddiamines); acetic anhydride and pyridine (in the case of the chemicalmethod); and toluene and xylene (in the case of the thermal method). Inthe precipitation method using a poor solvent, purification and dryingcan be carried out while removing the impurities. Consequently, it ispossible to improve the quality of the resulting polyimide resin (A).

<Second Method>

In the second method for synthesis (production) of the polyimide resin(A), an acid dianhydride component containing at least one aciddianhydride and an isocyanate component containing at least onediisocyanate are reacted with each other in an organic solvent. In thisprocess, as in the synthesis of the polyamic acid in the first method,substantially equimolar amounts of the acid dianhydride component andthe isocyanate component are mixed.

In the second method, the process for reaction of the individual monomercomponents is not particularly limited. In general, as in the synthesisof the polyamic acid described above, a process is used in whichsubstantially equimolar amounts of the acid dianhydride component andthe isocyanate component are dissolved in an organic solvent, and thenstirring is performed under controlled reaction conditions untilpolymerization is completed. By this process, it is possible to producea solution in which a polyimide is dissolved in an organic solvent(soluble polyimide solution) in one stage.

Although the reaction of the individual monomer components may beperformed in the absence of a catalyst, it is preferable to use acatalyst that catalyzes the reaction of the isocyanate component withthe active hydrogen compound. Examples of the catalyst include tertiaryamines, alkali metal compounds, alkaline-earth metal compounds, metals,such as cobalt, titanium, tin, and zinc, and semimetallic compounds. Inthe second method, the order of addition of the acid dianhydridecomponent and the isocyanate component is not particularly limited andmay be selected according to the synthesis method of the polyamic aciddescribed above.

In the second method, the synthesis conditions for synthesizing thepolyimide resin (A) are not particularly limited as long as a polyimideis sufficiently synthesized by polymerization of the monomer components.In the present invention, among the synthesis conditions, thetemperature conditions and the organic solvent used are preferablydefined as described below.

The temperature range for the synthesis reaction in the second method isnot particularly limited as long as the acid dianhydride component andthe isocyanate component can be polymerized. Usually, the temperature ispreferably in a range of 50° C. to 220° C. Additionally, the reactiontime is not particularly limited.

In the synthesis reaction of the second method, any solvent capable ofdissolving the resulting polyimide resin (A) sufficiently can be usedwithout limitation. As in the synthesis of the polyamic acid describedabove, from the standpoints that an increase in viscosity is preventedto facilitate stirring during the synthesis and that the resultingpolyimide resin (A) is easily dried, and the like, preferably, anorganic solvent that can dissolve the polyimide satisfactorily and thathas a boiling point as low as possible is selected. Thereby, theproduction process of the polyimide resin (A) can be performed moreefficiently.

Examples of the organic solvent which may be used in the synthesisreaction of the second method include, but are not limited to,amide-based organic solvents, such as N,N-dimethylformamide,N,N-dimethylacetamide, N,N-diethylacetamide,N,N-dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, andhexamethylphosphamide; lactam-based organic solvents, such asN-methylcaprolactam; urea-based organic solvents, such as1,3-dimethyl-2-imidazolidinone and tetramethylurea; hydrocarbon-basedorganic solvents, such as 1,2-dimethoxyethane,1,2-bis(2-methoxyethyl)ethane, and bis[2-(2-methoxyethoxy)ethane];ether-based organic solvents, such as bis(2-methoxyethyl) ether,bis[2-(2-methoxyethoxy)ethyl] ether, 1,3-dioxane, 1,4-dioxane,tetrahydrofuran, and diglyme; ester-based organic solvents, such asγ-butyrolactone; pyridine-based organic solvents, such as pyridine andpicoline; sulfur-based organic solvents, such as dimethyl sulfoxide,dimethyl sulfone, and sulfolane; nitro-based organic solvents, such asnitromethane, nitroethane, and nitrobenzene; and nitrile-based organicsolvents, such as acetonitrile. These organic solvents may be used aloneor two or more of these may be combined appropriately.

<Soluble Polyimide Solution>

In the preparation of the thermosetting resin composition of the presentinvention, the resulting polyimide resin (A) may be dissolved in adesired organic solvent to prepare a soluble polyimide solution usablein the preparation. The organic solvent used for the soluble polyimidesolution is not particularly limited as long as the solvent can dissolvethe resulting polyimide resin (A). Examples of the organic solventinclude the polar organic solvents used in the synthesis reaction of thepolyamic acid described above. These organic solvents may be used aloneor two or more of these may be combined appropriately.

The concentration of the soluble polyimide solution is not particularlylimited and may be determined appropriately depending on the application(intended use), method of use, etc. of the thermosetting resincomposition. Usually, the concentration is in a range of 1 to 30% byweight. The viscosity of the soluble polyimide solution is notparticularly limited. Usually, in an N-methyl-2-pyrrolidone solutioncontaining the soluble polyimide, the logarithmic viscosity number at30° C. is preferably in a range of 0.1 to 2.5 dl/g. If the logarithmicviscosity number is within this range, the molecular weight of thepolyimide resin (A) can generally be set at a suitable value.

The thermosetting resin composition of the present invention contains atleast one of the polyimide resins (A) described above as thepolyimide-based resin (A). The thermosetting resin composition maycontain two or more polyimide resins (A) or may contain a polyimideresin other than the polyimide resins (A). Furthermore, as the polyimideresin (A), a polyamic acid, which is a precursor before imidization, maybe used. Use of the imidized polyimide resin (A) instead of polyamicacid is preferable because reactions do not easily occur during mixingof the individual components and stability is high when thethermosetting resin composition is prepared.

(B) Phenol Resin

The phenol resin contained in the thermosetting resin compositionaccording to the first embodiment of the present invention will now bedescribed. Incorporation of the phenol resin component (B) containing atleast one phenol resin into the thermosetting resin composition of thepresent invention imparts plasticity to the thermosetting resincomposition and also imparts heat resistance to a cured resin obtainedby curing the thermosetting resin composition. Furthermore, the phenolresin enables the epoxy resin component (C), which will be describedbelow, to be cured efficiently when the thermosetting resin compositionis cured.

The phenol resin is not particularly limited. Examples thereof includephenol novolac-type phenol resins, cresol novolac-type phenol resins,bisphenol A novolac-type phenol resins, biphenol cresol novolac-typephenol resins, cresol/melamine copolymer-type phenol resins, andnaphthol/cresol copolymer-type phenol resins. Among the phenol resinsdescribed above, a phenol resin having at least one aromatic ring and/oraliphatic ring in its molecular chain is preferably used. Thereby, it ispossible to obtain compatibility with the polyimide resin component (A)and the epoxy resin component (C). It is also possible to impartexcellent heat resistance to a cured resin obtained by curing thethermosetting resin composition.

As the phenol resin having at least one aromatic ring and/or aliphaticring in its molecular chain, particularly preferred is at least onephenol resin selected from the group consisting of compounds havingstructures represented by the formulae:

(wherein a, b, c, d, and e each represent an integer of 1 to 10).

These phenol resins may be used alone or two or more of these may becombined appropriately.

With respect to the hydroxyl value (also referred to as “hydroxylequivalent”) of the phenol resin, the lower limit is preferably 90 ormore, more preferably 95 or more, and most preferably 100 or more. Theupper limit of the hydroxyl value of the phenol resin is preferably 300or less, more preferably 200 or less, and most preferably 150 or less.

If the hydroxyl value of the phenol resin becomes less than 90, theamount of the polar groups in the cured resin obtained by curing thethermosetting resin composition increases, resulting in degradation indielectric characteristics.

That is, the dielectric constant and the dielectric loss tangent of thecured resin increase. On the other hand, if the hydroxyl value exceeds200, the crosslinking density in the cured resin decreases, resulting indegradation in heat resistance.

(C) Epoxy Resin Component

The epoxy resin contained in the thermosetting resin composition of thepresent invention will now be described. Incorporation of an epoxy resincomponent (C) containing at least one epoxy resin into the thermosettingresin composition of the present invention imparts heat resistance andinsulating properties to a cured resin obtained by curing thethermosetting resin composition and also provides adhesiveness onconductors, such as metal foils, and circuit boards.

The epoxy resin is not particularly limited. Examples thereof includeepoxy resins, such as bisphenol-type epoxy resins, bisphenol Anovolac-type epoxy resins, phenol novolac-type epoxy resins, alkylphenol novolac-type epoxy resins, polyglycol-type epoxy resins, cyclicaliphatic epoxy resins, cresol novolac-type epoxy resins,glycidylamine-type epoxy resins, naphthalene-type epoxy resins,urethane-modified epoxy resins, rubber-modified epoxy resins, andepoxy-modified polysiloxanes; and halogenated epoxy resins obtained byhalogenation of these epoxy resins.

Among the epoxy resins described above, an epoxy resin having at leastone aromatic ring and/or aliphatic ring in its molecular chain ispreferably used. Such an epoxy resin is easily available and excellentin compatibility with the polyimide resin component (A) and the phenolresin component (B), and can impart excellent heat resistance andinsulating properties to the cured resin. As the epoxy resin having atleast one aromatic ring and/or aliphatic ring in its molecular chain,particularly preferred is at least one epoxy resin selected from thegroup consisting of compounds having structures represented by theformulae:

[Chemical formula 19]

(wherein g, h, i, j, and k each represent an integer of 1 to 10).

With respect to the epoxy resin contained in the thermosetting resincomposition, in order to achieve highly reliable electrical insulation,a high-purity epoxy resin is preferably used. That is, the content ofhalogens and alkali metals in the epoxy resin is preferably 25 ppm orless, and more preferably 15 ppm or less, when extracted at 120° C. and2 atm. If the content of halogens and alkali metals exceeds 25 ppm,reliability of electrical insulation of a cured resin obtained by curingthe thermosetting resin composition is impaired.

With respect to the epoxy value (also referred to as “epoxy equivalent”)of the epoxy resin, the lower limit is preferably 150 or more, morepreferably 170 or more, and most preferably 190 or more. Furthermore,the upper limit of the epoxy value of the epoxy resin is preferably 700or less, more preferably 500 or less, and most preferably 300 or less.

If the epoxy value of the epoxy resin becomes less than 150, the amountof the polar groups in the cured resin obtained by curing thethermosetting resin composition increases, resulting in degradation indielectric characteristics. That is, the dielectric constant and thedielectric loss tangent of the cured resin increase. On the other hand,if the epoxy value exceeds 700, the crosslinking density in the curedresin decreases, resulting in degradation in heat resistance.

(F) Other Components

The thermosetting resin composition according to the first embodiment ofthe present invention may contain, according to need, a curing agent(F-1) for the epoxy resin component, a curing accelerator (F-2) foraccelerating the reaction of the epoxy resin component with the curingagent, and other thermosetting components, in addition to the phenolresin component (B) and the epoxy resin component (C).

(F-1) Curing Agent

The curing agent is not particularly limited. Examples thereof includearomatic diamine compounds, such as bis(4-aminophenyl) sulfone,bis(4-aminophenyl)methane, 1,5-diaminonaphthalene, p-phenylenediamine,m-phenylenediamine, o-phenylenediamine, 2,6-dichloro-1,4-benzenediamine,1,3-di(p-aminophenyl)propane, and m-xylenediamine; aliphatic aminecompounds, such as ethylenediamine, diethylenediamine,tetraethylenepentaamine, diethylaminopropylamine, hexamethylenediamine,menthane diamine, isophorone diamine,bis(4-amino-3-methyldicyclohexyl)methane, polymethylenediamine, andpolyetherdiamine; polyaminoamide-based compounds; aliphatic acidanhydrides, such as dodecylsuccinic anhydride, poly(adipic anhydride),and poly(azelaic anhydride); alicyclic acid anhydrides, such ashexahydrophthalic anhydride and methylhexahydrophthalic acid; aromaticacid anhydrides, such as phthalic anhydride, trimellitic anhydride,benzophenonetetracarboxylic acid, ethylene glycol bistrimellitate, andglycerol tristrimellitate; amino resins; urea resins; melamine resins;dicyandiamide; dihydrazine compounds; imidazole compounds; salts ofLewis acids and Broensted acids; polymercaptan compounds; and isocyanateand blocked isocyanate compounds.

These curing agents may be used alone or in combination of two or more.The curing agent is preferably used in an amount of 1 part by weight to100 parts by weight based on 100 parts by weight of total epoxy resin.

(F-2) Curing Accelerator

Examples of the curing accelerator include, but are not limited to,phosphine compounds, such as triphenylphosphine; amine compounds, suchas tertiary amines, trimethanolamine, triethanolamine, andtetraethanolamine; borate compounds such as,1,8-diazabicyclo[5,4,0]-7-undecenium tetraphenyl borate; imidazoles,such as imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole,2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole,2-heptadecylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, and2-phenyl-4-methylimidazole; imidazolines, such as 2-methylimidazoline,2-ethylimidazoline, 2-isopropylimidazoline, 2-phenylimidazoline,2-undecylimidazoline, 2,4-dimethylimidazoline, and2-phenyl-4-methylimidazoline.

These curing accelerators may be used alone or in combination of two ormore. The curing accelerator is preferably used in an amount of 0.01parts by weight to 10 parts by weight based on 100 parts by weight oftotal epoxy resin.

Furthermore, examples of the thermosetting component which may be usedinclude, in order to improve various characteristics, such asadhesiveness, heat resistance, and processability, of the thermosettingresin composition or a cured resin of the thermosetting resincomposition, thermosetting resins, such as bismaleimide resins,bisallylnadiimide resins, acrylic resins, methacrylic resins, curablehydrosilyl resins, curable allyl resins, and unsaturated polyesterresins; and reactive side-chain group-containing thermosetting polymershaving reactive groups, such as an allyl group, a vinyl group, analkoxysilyl group, or a hydrosilyl group, in side chains or in terminiof the molecular chain. These thermosetting components may be used aloneor two or more of these may be combined appropriately.

Furthermore, the curing agent, the curing accelerator, and thethermosetting component are preferably incorporated into thethermosetting resin composition within such a range that the dielectriccharacteristics of a cured resin obtained by curing the thermosettingresin composition are not impaired.

Second Embodiment

A thermosetting resin composition according to a second embodiment ofthe present invention contains at least a polyimide resin (A) containingat least one polyimide resin, a phosphazene compound (D) containing atleast one phosphazene compound, and a cyanate ester compound (E)containing at least one cyanate ester compound. The phosphazene compound(D) includes a phenolic hydroxyl group-containing phenoxyphosphazenecompound (D-1) and/or a crosslinked phenoxyphosphazene compound (D-2)prepared by crosslinking the phenoxyphosphazene compound (D-1), thecrosslinked phenoxyphosphazene compound (D-2) having at least onephenolic hydroxyl group.

Since the thermosetting resin composition according to the presentinvention contains the polyimide resin (A), it is possible to impartheat resistance to the thermosetting resin composition. Furthermore, itis possible to impart flexibility, excellent mechanical characteristics,and chemical resistance to a cured resin obtained by curing thethermosetting resin composition. It is also possible to impart excellentdielectric characteristics, i.e., a low dielectric constant and a lowdielectric loss tangent in the GHz range, to the cured resin.

(A) Polyimide Resin

As the polyimide resin (A) in the second embodiment, the polyimide resin(A) described in the first embodiment can be used.

In the thermosetting resin composition according to the secondembodiment of the present invention, the amount of the polyimide resinto be mixed is not particularly limited, but is preferably in the rangedescribed below. That is, the lower limit is preferably 20% by weight ormore, and more preferably 30% by weight or more, based on 100% by weightof total thermosetting resin composition. On the other hand, the upperlimit is preferably 80% by weight or less, and more preferably 60% byweight or less. If the amount of the polyimide resin (A) mixed is withinthe range described above, it is possible to impart excellentprocessability to the thermosetting resin composition and excellentphysical properties, such as dielectric characteristics and heatresistance, to a cured resin (cured object) obtained by curing thethermosetting resin composition.

(D) Phosphazene Compound

In the thermosetting resin composition according to the secondembodiment of the present invention, a phenolic hydroxylgroup-containing compound, i.e., the phenoxyphosphazene compound (D-1)and/or the crosslinked phenoxyphosphazene compound (D-2), is used. Thecrosslinked phenoxyphosphazene compound (D-2) is a phosphazene compoundprepared by crosslinking the phenoxyphosphazene compound (D-1).

Incorporation of the phenoxyphosphazene compound (D-1) and/or thecrosslinked phenoxyphosphazene compound (D-2) can impart flameretardance to the resulting thermosetting resin composition withoutimpairing heat resistance. In particular, since the phosphazene compoundused in the present invention has a phenolic hydroxyl group in itsmolecule, compatibility with the polyimide resin (A) can be remarkablyimproved because of the phenolic hydroxyl group. Consequently, in theresulting thermosetting resin composition, it is possible to prevent theflame retardant from being easily precipitated on the surface (i.e.,occurrence of bleeding or juicing), and thus flame retardance can befurther improved.

Moreover, since the phenolic hydroxyl group is contained in themolecule, compatibility with the imide resin is significantly improved,and when the thermosetting resin composition is cured, a networkstructure can be formed by reaction with the cyanate ester compound (E),which will be described below. Consequently, curing can be performedefficiently, and a cured object having excellent heat resistance can beobtained. Furthermore, alkali-solubility can be improved compared withthe conventional phosphazene compound.

<(D-1) Phenoxyphosphazene Compound>

The phenoxyphosphazene compound (D-1) used in the present invention isnot particularly limited as long as phosphazene compound has a phenolichydroxyl group. Specifically, at least one of the cyclicphenoxyphosphazene compound (D-11) and the linear phenoxyphosphazenecompound (D-12) is preferably used.

The cyclic phenoxyphosphazene compound (D-11) has a structurerepresented by general formula (2):

(wherein m represents an integer of 3 to 25; R¹ and R² each represent aphenyl group or a hydroxyphenyl group (—C6H4OH); and at least onehydroxyphenyl group is contained per molecule).

The linear phenoxyphosphazene compound (D-12) has a structurerepresented by general formula (3):

(wherein n represents an integer of 3 to 10,000; R³ and R⁴ eachrepresent a phenyl group or a hydroxyphenyl group; at least onehydroxyphenyl group is contained per molecule; R⁵ represents—N═P(OC₆H₅)₃, —N═P(OC₆H₅)₂(OC₆H₄OH), —N═P(OC₆H₅)(OC₆H₄OH)₂,—N═P(OC₆H₄OH)₃, —N═P(O)OC₆H₅, or —N═P(O)(OC₆H₄OH); and R⁶ represents—P(OC₆H₅)₄, —P(OC₆H₅)₃(OC₆H₄OH), —P(OC₆H₅)₂(OC₆H₄OH)₂,—P(OC₆H₅)(OC₆H₄OH)₃, —P(OC₆H₄OH)₄, —P(O)(OC₆H₅)₂, —P(O)(OC₆H₅)(OC₆H₄OH),or —P(O)(OC₆H₄OH)₂).

The cyclic phenoxyphosphazene compound (D-11) and the linearphenoxyphosphazene compound (D-12) have excellent compatibility with thepolyimide resin (A) described above and the other components (D), whichwill be described below, and also can impart excellent heat resistanceto a cured object obtained by curing the resulting thermosetting resincomposition.

The method for producing the cyclic phenoxyphosphazene compound (D-11)or the linear phenoxyphosphazene compound (D-12) is not particularlylimited. Specifically, these compounds can be produced, for example, bythe method described in any of the documents described below.

-   Document A: Masaaki Yokoyama, et al., Kogyo Kagaku Zasshi, Vol. 67,    No. 9, p. 1378 (1964)-   Document B: Tomoya Okuhashi, et al., Kogyo Kagaku Zasshi, Vol. 73,    No. 6, p. 1164 (1970)-   Document C: Japanese Unexamined Patent Application Publication No.    58-219190-   Document D: Alessandro Medici, et. al., Macromolecules, Vol. 25, No.    10, p. 2569 (1992)-   Document E: Japanese Unexamined Patent Application Publication No.    54-145394-   Document F: Japanese Unexamined Patent Application Publication No.    54-145395

For example, a compound in which one hydroxyl group of a dihydric phenolis protected with a methyl group or a benzyl group (for the convenienceof description, referred to as a “protected phenol compound”), such as4-methoxyphenol or 4-(benzyloxy)phenol, is synthesized, and then analkali metal salt (e.g., lithium salt, sodium salt, or potassium salt)of the protected phenol compound is produced. The resulting alkali metalsalt of the protected phenol compound (alkali metal salt of4-methoxyphenol or alkali metal salt of 4-(benzyloxy)phenol) is reactedwith phosphonitrilic chloride which is described in each of Documents Eand F. Subsequently, by reaction with pyridine hydrohalide, borontribromide, or the like, the methyl group or the benzyl group is removedto deprotect the hydroxyl group. The phenoxyphosphazene compound isthereby synthesized.

Furthermore, with respect to the phenoxyphosphazene compounds, in orderto produce a compound having a phenoxy group partially substituted withthe hydroxyl group, an alkali metal salt of the protected phenolcompound and/or an alkali salt of hydroxyalkylphenol are prepared. Whenthe resulting alkali metal salts are allowed to react withphosphonitrilic chloride, an alcohol-based or phenol-based alkali metalsalt is simultaneously used.

<Example of Synthesis (Production) of Phenoxyphosphazene Compound (D-1)>

A specific example of a method for synthesizing (producing) the cyclicphenoxyphosphazene compound (D-11) or the linear phenoxyphosphazenecompound (D-12) will be described below.

First, at least one dichlorophosphazene compound selected from the groupconsisting of cyclic dichlorophosphazene compounds represented bygeneral formula (12):

(wherein m represents an integer of 3 to 25) and straight-chain orlinear dichlorophosphazene compounds represented by general formula(13):

(wherein X² represents —N═PCl₃ or —N═P(O)Cl; Y² represents —PCl₄ or—P(O)Cl₂; and n represents an integer of 3 to 10,000) is used as astarting phosphazene compound.

The compound represented by general formula (12) or (13) is allowed toreact with alkali metal phenolates represented by general formulae (14)and (15):

(in each formula, M represents an alkali metal). Additionally, in thealkali metal phenolate represented by general formula (15), the positionof the alkyloxy group (methoxy group) is not particularly limited.

By the reaction described above, the phenyl group and the methoxyphenylgroup can be introduced into the structure represented by generalformula (12) or (13). At this stage, in the structure represented byformula (12) or (13), at least one methoxyphenyl group must beintroduced per molecule. In other words, when the compound representedby general formula (12) or (13) is allowed to react with the compoundsrepresented by general formulae (14) and (15), the reaction conditionsincluding the amount (molar ratio equivalent) of the compoundrepresented by general formula (15) must be set so that at least onemethoxyphenyl group is introduced per molecule. The details of thereaction conditions are not particularly limited, and known conditionsmay be used.

By reaction of the resulting compound with pyridine hydrohalide, borontribromide, or the like, the methoxyphenyl group is removed to deprotectthe hydroxyl group. As a result, the cyclic phenoxyphosphazene compound(D-11) represented by general formula (2) or the linearphenoxyphosphazene compound (D-12) represented by general formula (3)can be synthesized.

<(D-2) Crosslinked Phenoxyphosphazene Compound>

As described above, the crosslinked phenoxyphosphazene compound (D-2)has at least one phenolic hydroxyl group and is a compound prepared bycrosslinking the phenoxyphosphazene compound (D-1). The crosslinkedphenoxyphosphazene compound (D-2) is prepared by crosslinking thephenoxyphosphazene compound (D-1) with a known crosslinking group, andpreferably with a phenylene-based crosslinking group.

The phenylene-based crosslinking group is a crosslinking groupcontaining a phenyl group in its structure. Specifically, for example, aphenylene-based crosslinking group contains at least any one ofo-phenylene group, m-phenylene group, and p-phenylene group representedas follows:

and a bisphenylene group represented by general formula (4):

(wherein R⁷ represents —C(CH₃)₂—, —SO₂—, —S—, or —O—; and p represents 0or 1).

In the present invention, when the crosslinked phenoxyphosphazenecompound (D-2) is synthesized (produced), as the phenoxyphosphazenecompound, any corresponding compound may be used. However, preferably,the cyclic phenoxyphosphazene compound (D-11) and/or the linearphenoxyphosphazene compound (D-12) are used. In such a case, preferably,the phenylene-based crosslinking group is used as the crosslinkinggroup.

Furthermore, on the conditions that (1) the cyclic phenoxyphosphazenecompound (D-11) and/or linear phenoxyphosphazene compound (D-12) areused as the phenoxyphosphazene compound and (2) the phenylene-basedcrosslinking group is used as the crosslinking group (2), crosslinkingconditions are preferably set so as to satisfy the conditions (3) and(4) described below.

That is, preferably, (3) the phenylene-based crosslinking group liesbetween two oxygen atoms of the phenoxyphosphazene compound (D-1)(cyclicphenoxyphosphazene compound (D-11) and/or linear phenoxyphosphazenecompound (D-12)), the phenyl group and the hydroxyphenyl group beingseparated from the oxygen atoms; and (4) the content of the phenyl groupand the hydroxyphenyl group in the crosslinked phenoxyphosphazenecompound is in a range of 50% to 99.9% based on the total number ofphenyl groups and hydroxyphenyl groups contained in thephenoxyphosphazene compound.

If a crosslinked phenoxyphosphazene compound (D-2) that satisfies theconditions (1) to (4) is used, it is possible to further improve flameretardance in the resulting thermosetting resin composition.Additionally, the crosslinked phenoxyphosphazene compound that satisfiesthe conditions (1) to (4) is referred to as a “phenylene-basedcrosslinked phenoxyphosphazene compound (D-21)”.

<Example of Synthesis (Production) of Crosslinked PhenoxyphosphazeneCompound (D-2)>

The production method for the crosslinked phenoxyphosphazene compound(D-2) is not particularly limited. An example of the synthesis methodwill be described below in which the phenylene-based crosslinkedphenoxyphosphazene compound (D-21) is taken as an example.

First, a dichlorophosphazene compound represented by general formula(12) or (13) is allowed to react with alkali metal phenolates. As thealkali metal phenolates used in this step, in addition to the alkalimetal phenolates represented by general formulae (14) and (15), alkalimetal diphenolates represented by general formulae (16) and (17):

(wherein M represents an alkali metal; R⁷ represents —C(CH3)2- , —SO2- ,—S—, or —O—; and p represents 0 or 1) are used at the same time.

The resulting compound has a structure in which the methoxyphenyl group(and the phenyl group) is introduced into the structure represented bygeneral formula (12) or (13) and in which the structure represented bygeneral formula (12) or (13) is crosslinked by the alkali metaldiphenolates represented by general formulae (16) and (17).Subsequently, by reaction with pyridine hydrohalide or boron tribromide,the methyl group or the benzyl group is removed to deprotect thehydroxyl group. As a result, a compound in which the phenoxyphosphazenecompound represented by general formula (2) and/or (3) is crosslinkedwith an aromatic diol, i.e., the phenylene-based crosslinkedphenoxyphosphazene compound (D-21), can be produced.

The amount of the phenoxyphosphazene compound (including the crosslinkedcompound) to be added is not particularly limited, but preferably in arange of 0.1% to 50% by weight based on 100% by weight of the totalweight of the thermosetting resin composition. If the amount becomesless than 0.1% by weight, the flame retardance-imparting effect may bedecreased. If the amount exceeds 50% by weight, adhesiveness andmechanical characteristics may be degraded.

In particular, in the present invention, the mixing ratio by weight(B)/[(A)+(B)+(C)] is preferably in a range of 0.01 to 0.4, and morepreferably in a range or 0.05 to 0.4, the mixing ratio by weight beingthe ratio of the weight of the phosphazene compound (B) to the totalweight of the polyimide resin (A), the phosphazene compound (B), and thecyanate ester compound (E). If the mixing ratio by weight becomes lessthan 0.01, the flame retardance-imparting effect may be decreased. Ifthe mixing ratio by weight exceeds 0.4, heat resistance, such asresistance to soldering heat, adhesiveness, and dielectriccharacteristics may be degraded.

Furthermore, with respect to the mixing ratio by weight (A)/[(B)+(C)],the mixing ratio by weight being the ratio of the weight of thepolyimide resin (A) to the total weight of the phosphazene compound (B)and the cyanate ester compound (E), the lower limit is preferably 0.4 ormore, and particularly preferably 0.5 or more, and the upper limit ispreferably 2.0 or less, and particularly preferably 1.5 or less.

If the mixing ratio by weight becomes less than 0.4, i.e., if thecontent of the phosphazene compound component (B) and the cyanate estercompound component (E) in the thermosetting resin composition becomesrelatively larger than the content of the polyimide resin component (A),in a resin sheet before curing, flowability increases and minimumcomplex viscosity decreases.

Furthermore, in a resin sheet after curing, although heat resistance,which is represented by a modulus of elasticity, a coefficient of linearexpansion, and the like, at high temperatures increases, it becomesdifficult to achieve a low dielectric constant and a low dielectric losstangent (hereinafter referred to as excellent dielectriccharacteristics) in the GHz (gigahertz) range. On the other hand, if themixing ratio by weight exceeds 2.0, i.e., if the content of thepolyimide resin component (A) in the thermosetting resin compositionbecomes relatively larger than the content of the phosphazene compoundcomponent (B) and the cyanate ester compound component (E), althoughexcellent dielectric characteristics can be exhibited in the cured resinin the GHz range, adhesiveness between the thermosetting resincomposition and a conductor or a circuit board, and processabilityduring bonding between the thermosetting resin composition and aconductor or a circuit board are degraded.

In the thermosetting resin composition of the present invention, bysetting the mixing ratio by weight in the range described above, a curedresin obtained by curing the thermosetting resin composition exhibitsexcellent dielectric characteristics even in the GHz range. That is,with respect to the dielectric characteristics of a cured resin obtainedby heating the thermosetting resin composition at a temperature of 150°C. to 250° C. for 1 to 5 hours, the dielectric constant is 3.3 or lessand the dielectric loss tangent is 0.02 or less at a frequency of 1 to10 GHz. If the dielectric constant and the dielectric loss tangent arein the ranges described above, when the thermosetting resin compositionof the present invention is used as a protective material or aninterlayer insulating material in a circuit board, it is possible toensure electrical insulation of the circuit board and to preventdecreases in the transmission speed of signals and loss of signals inthe circuit on the circuit board. Therefore, a highly reliable circuitboard can be provided.

(E) Cyanate Ester Compound

The cyanate ester compound (E) according to the present invention willnow be described. The cyanate ester compound (E) used in the presentinvention is not particularly limited as long as the compound has acyanato group and an ester bond. For example, preferably used is atleast one cyanate ester compound selected from cyanate ester compoundsrepresented by general formula (18):

(wherein each R¹¹ represents a single bond, a divalent organic grouphaving at least one aromatic ring, —CH2- , —C(CH3)2- , C(CF3)2- ,—CH(CH3)- , —CH(CF3)—, —SO2- , —S—, or —O—; o, p, and q eachindependently represent an integer of 0 to 3; and R¹² and R¹³ eachindependently represent an organic group selected from —H, —CH3, and—CF3).

By using the cyanate ester compound represented by general formula (18),it is possible to impart excellent heat resistance to the thermosettingresin composition.

Among the cyanate ester compounds represented by general formula (18),in view of high compatibility with the soluble polyimide resin and easyavailability, more preferably, at least one cyanate ester compoundselected from compounds represented by the group of general formulae

(wherein r represents 0 to 4) is used, and particularly preferably, acyanate ester compound represented by general formula (19):

is used.

As the cyanate ester compound (E) used for the thermosetting resincomposition of the present invention, any one of the cyanate estercompounds can be used as a monomer. It is also possible to use thecyanate ester compound as an oligomer which is prepared by a partialreaction of the cyanato group of the monomer by heating or the like.Furthermore, the oligomer and the monomer can be used together. Examplesof the oligomer of the cyanate ester compound include BA200 (trade name)manufactured by Lonza Inc. and Arocy B-30, B-50, M-30, and M-50 (tradename) manufactured by Asahi-Ciba Ltd. These cyanate ester compounds (E)may be used alone or two or more of these may be combined appropriately.

(G) Other Components

The thermosetting resin composition according to the present inventionmay contain other components (D), in addition to the polyimide resin(A), the phosphazene compound (B), and the cyanate ester compound (E).The other components (G) are appropriately selected depending on theapplication of the resulting thermosetting resin composition and are notparticularly limited. Specifically, examples of the other componentsinclude a curing catalyst (G-1) for improving a thermosetting propertyand other resins (G-2).

(G-1) Curing Catalyst

In the thermosetting resin composition of the present invention, thecyanate ester compound (E) must be subjected to reaction to such anextent that excellent dielectric characteristics can be exhibited aftercuring. In some case, the reaction of the cyanate ester compound (E)requires a high temperature of 200° C. or more and a time of 2 hours ormore. Therefore, in order to promote the reaction of the cyanate estercompound (E), a curing catalyst (G-1) is preferably used.

Any compound capable of promoting reaction of the cyanate ester compound(E) can be used as the curing catalyst (G-1) without limitation.Specific examples thereof include metal-based catalysts, such aszinc(II) acetylacetonate, zinc naphthenate, cobalt(II) acetylacetonate,cobalt(III) acetylacetonate, cobalt naphthenate, copper(II)acetylacetonate, and copper naphthenate; and hydroxyl group-containingorganic compounds, such as N-(4-hydroxyphenyl)maleimide,p-tert-octylphenol, cumylphenol, and phenol resins. These curingcatalysts (G-1) may be used alone or two or more of these may becombined appropriately.

Among the curing catalyst (G-1) described above, from the standpointthat curing can be further promoted, use of the metal-based catalyst ispreferable. In particular, zinc(II) acetylacetonate and copper(II)acetylacetonate are preferable. The amount of the curing catalyst (G-1)mixed varies depending on the types of the curing catalyst (G-1) usedand the extent of the promotion of reaction. For example, if the curingcatalyst is a metal-based curing catalyst, the curing catalyst is usedpreferably in an amount of 0.001 parts by weight to 0.1 parts by weightbased on 100 parts by weight of the cyanate ester compound (E). If thecuring catalyst is an organic compound, the curing catalyst is usedpreferably in an amount of 0.1 parts by weight to 20 parts by weightbased on 100 parts by weight of the cyanate ester compound (E). Inparticular, when zinc(II) acetylacetonate or copper(II) acetylacetonateis used, the curing catalyst is used preferably in an amount of 0.001parts by weight to 0.05 parts by weight based on 100 parts by weight ofthe cyanate ester compound (E). If the amount of the curing catalyst(D-1) used is below the range described above, the effect of promotingreaction is not easily obtained. If the amount exceeds the rangedescribed above, there is a possibility that storage stability of theresulting thermosetting resin composition will be impaired, which isundesirable.

<(G-2) Other Resins>

The thermosetting resin composition of the present invention may containother resins (G-2) as thermosetting components, besides the cyanateester compound (E). The other resins (G-2) are not particularly limitedas long as the resins improve various characteristics, such asadhesiveness, heat resistance, and processability. Preferably, the otherresins are selected to such an extent that the dielectriccharacteristics of the thermosetting resin composition are not impaired.Examples of the other resins (G-2) include thermosetting resins, such asbismaleimide resins, bisallylnadiimide resins, phenol resins, epoxyresins, acrylic resins, methacrylic resins, curable hydrosilyl resins,curable allyl resins, and unsaturated polyester resins; and reactiveside-chain group-containing thermosetting polymers having reactivegroups, such as an epoxy group, an allyl group, a vinyl group, analkoxysilyl group, or a hydrosilyl group, in side chains or in terminiof the molecular chain. In the thermosetting resin composition, theseresins may be used alone or in appropriate combination.

<Production of Thermosetting Resin Composition>

The method for producing (preparing) the thermosetting resin compositionof the present invention, i.e., the method for compounding theindividual components described above, is not particularly limited. Forexample, in a method, a solution of the thermosetting resin compositionis prepared using an organic solvent that satisfactorily dissolves theindividual components. More specifically, for example, the individualcomponents are added to a suitable solvent, followed by stirring toobtain a solution of the thermosetting resin composition. Alternatively,the individual components are dissolved in suitable solvents to preparerespective solutions of the components, and these solutions are mixed toobtain a solution of the thermosetting resin composition.

As the organic solvent used in this process, a known organic solventused for polyimide resins can be used. Examples of the organic solventinclude aromatic hydrocarbons, ketones, esters, ethers (e.g., cyclicethers and glycol ethers), N-substituted amides, alcohols, carboxylicacids, amines, and chlorine-based solvents. In particular, a low-boilingorganic solvent having a boiling point of 170° C. or less, preferably160° C. or less, can be preferably used.

Examples of the low-boiling organic solvent which may be preferably usedinclude ethers, such as cyclic ethers, e.g., tetrahydrofuran, dioxolane,and dioxane, and linear ethers, e.g., ethylene glycol dimethyl ether,triglyme, diethylene glycol, Ethyl Cellosolve, Methyl Cellosolve,diethyl ether, and various types of propylene glycol ether; alcohols,such as methanol, ethanol, isopropyl alcohol, and butanol; ketones, suchas acetone, methyl ethyl ketone, and methyl isobutyl ketone;cycloalkanes, such as cyclopentanone and cyclohexanone; and esters, suchas ethyl acetate. Furthermore, any of mixed solvents prepared by mixingethers with toluene, xylenes, glycols, N,N-dimethylformamide,N,N-dimethylacetamide, N-methylpyrrolidone, cyclic siloxane, linearsiloxane or the like can also be preferably used. These organic solventsmay be used alone or two or more of these may be appropriately mixed foruse. Furthermore, with respect to an organic solvent compatible withwater, the organic solvent may be used as a mixture with water.

As described above, the thermosetting resin composition according to thepresent invention may be in the form of a solution in which thethermosetting resin composition is dissolved in an organic solvent(preferably a low-boiling organic solvent). Such a solution of thethermosetting resin composition can be suitably used as a coatingmaterial. Consequently, in the thermosetting resin composition of thepresent invention, the organic solvent and water may be contained inother components (H). In a typical example of the solution of thethermosetting resin composition according to the present invention, thethermosetting resin composition is dissolved in dimethylformamide ordimethylacetamide in an amount of preferably 1% by weight or more, andmore preferably 5% by weight or more.

<Use of Thermosetting Resin Composition>

Use of the thermosetting resin composition according to the presentinvention is not particularly limited. Specifically, examples of the useinclude resin films and resin sheets formed using the thermosettingresin composition, and resin preparations.

The resin films can be suitably used, for example, as adhesive sheetsfor printed circuit boards, coverlay films, insulative circuitprotective film for printed circuit boards, and substrates for printedcircuit boards. The resin preparations can be suitably used as adhesivesfor printed circuit boards, sealing materials for printed circuitboards, protecting agents for circuits, and cover ink.

Furthermore, another use of the present invention is for a multilayerbody which includes at least one resin layer formed of the thermosettingresin composition or using a resin film or a resin preparation preparedusing the thermosetting resin composition. The multilayer body can besuitably used, for example, as a circuit board or a multilayer printedcircuit board.

The resin film, the resin preparation, and the multilayer body will bedescribed based on a specific example.

The thermosetting resin composition according to the present inventioncan be used as a resin preparation in a solution state. Thethermosetting resin composition may also be used as a resin preparationby incorporation of various solvents and additives according to need.The resin preparation containing the thermosetting resin composition ofthe present invention can be used as a coating material or varnish,which, for example, may be impregnated into various fibers, such asglass cloths, glass mats, aromatic polyamide fiber cloths, and aromaticpolyamide fiber mats. By semi-curing the thermosetting resin compositionthus impregnated into the fibers, it is possible to obtainfiber-reinforced resin sheets.

Furthermore, the thermosetting resin composition of the presentinvention may be preliminarily formed into sheets and then be used asresin films or resin sheets. Specific examples thereof include (1) aone-layer sheet composed of only the thermosetting resin composition,(2) a two-layer or three-layer sheet formed by disposing a resin layercomposed of the thermosetting resin composition to one surface or bothsurfaces of a film serving as a base (film base), and (3) a multilayerbody in which film bases and resin layers composed of the thermosettingresin composition are alternately laminated.

The resin sheet can be produced by a method in which the solution of thethermosetting resin composition or the resin preparation is flow-cast orapplied onto a surface of a support, followed by drying, to form into afilm. The film of the resulting thermosetting resin composition (resinfilm) is in a semi-cured state (stage B). Thus, by separating thesemi-cured resin film from the support, the one-layer sheet can beobtained. Furthermore, the multilayer body can be produced by a methodin which the solution of the thermosetting resin composition or theresin preparation is flow-cast or applied onto a surface of the filmbase, followed by drying, and this operation is repeated.

Any known resin film or resin sheet can be used as a material for thefilm base without limitation. For example, if a metal, such as copper oraluminum, is used as the film base, a metal-clad laminate can beproduced. That is, the metal-clad laminate is a multilayer bodyincluding at least one resin layer composed of the thermosetting resincomposition and at least one metal layer. The resin layer may bedisposed only one surface of the metal layer. Alternatively, metallayers and resin layers may be alternately laminated.

The metal-clad laminate may be produced by flow-casting or applying thesolution of the thermosetting resin composition or the resin preparationonto a surface of a metal layer, followed by drying, as described above.Alternatively, the metal-clad laminate may be produced by bonding ametal foil to the resin sheet, or by forming a metal layer on thesurface of the resin sheet by chemical plating, sputtering, or the like.Furthermore, when the metal layer is composed of a metal that can beused as a conductor for a circuit board, the metal layer of themetal-clad laminate may be subjected to metal etching using a dry filmresist, a liquid resist, or the like to form a circuit having a desiredpattern (hereinafter referred to as a patterned circuit). Consequently,by forming a patterned circuit in the metal layer of the metal-cladlaminate and providing a resin layer composed of the thermosetting resincomposition of the present invention, the resulting multilayer body canbe used as a circuit board, such as a flexible printed circuit board ora build-up circuit board.

When a metal layer provided with a patterned circuit is used as themetal layer, the semi-cured resin sheet described above may be used as aresin layer. Since the semi-cured resin sheet composed of thethermosetting resin composition of the present invention has a moderatedegree of flowability, the patterned circuit can be suitably embeddedwhen thermal press bonding, such as thermal pressing, lamination(thermal lamination), or hot roll lamination, is performed. As a result,the metal layer and the resin layer can be bonded togethersatisfactorily.

The process temperature of the thermal press bonding is not particularlylimited as long as press bonding can be performed sufficiently. Theprocess temperature is in a range of preferably 50° C. to 200° C., morepreferably 60° C. to 180° C., and particularly preferably 80° C. to 130°C. At a process temperature exceeding 200° C., the resin layer may becured during thermal press bonding. On the other hand, at a processtemperature less than 50° C., the flowability of the resin layer is low,and it is difficult to embed the patterned circuit.

The resin layer disposed on the patterned circuit serves as a protectivematerial for protecting the patterned circuit or as an interlayerinsulating material in a multilayer circuit board. Therefore, after thepatterned circuit is embedded, it is preferable to completely cure theresin layer by exposure treatment, thermal curing, or the like.

Additionally, when the thermosetting resin composition of the presentinvention is cured, in order to allow curing reaction of the cyanateester compound component (E) to proceed sufficiently, preferably,post-heating is performed after bonding of the metal layer to the resinlayer. The conditions of the post-heating are not particularly limited.Preferably, the post-heating is performed at 150° C. to 200° C. for 10minutes to 3 hours.

As described above, the thermosetting resin composition of the presentinvention is excellent in dielectric characteristics, heat resistance,and flame retardance because of the individual components containedtherein, and excellent in processability and handleability because ofthe thermosetting components contained therein, these various physicalproperties being well-balanced. Therefore, it is possible tosufficiently overcome the problems associated with the conventionalinsulating layers. As a result, the thermosetting resin composition canbe suitably used for manufacturing various laminated structures, forexample, laminated materials, such as flexible printed circuit boards(FPCs) and multilayer build-up circuit boards, which require a lowdielectric constant and a low dielectric loss tangent.

Furthermore, the thermosetting resin composition of the presentinvention may, of course, contain components other than those describedabove as long as its characteristics are not degraded. Similarly, in thethermosetting resin composition of the present invention, process stepsother than those described above may be, of course, involved.

EXAMPLES

While the present invention will be described more specifically based onexamples and comparative examples below, it is to be understood that thepresent invention is not limited thereto. Persons skilled in the art mayapply various changes, modifications, and alternations without deviatingfrom the scope of the present invention.

The flowability, laminatability, and calculation of the volatilecomponent content of a resin sheet composed of the thermosetting resincomposition of the present invention and the dielectric characteristics,glass transition temperature, resistance to soldering heat, and flameretardance of a cured resin sheet formed by thermally curing the resinsheet were measured and evaluated as described below.

[Flowability]

With respect to resin sheets before thermal curing, using a dynamicviscoelasticity analyzer (CVO, manufactured by Bohling Corp.) in theshear mode, the complex viscosity (Pa·s) was measured under theconditions described below. The complex viscosity of each resin sheetwas evaluated based on the lowest complex viscosity in the measurementtemperature range.

Measurement frequency: 1 Hz

Heating rate: 3.5° C./min

Sample measured: Circular resin sheet with a diameter of 3 mm

[Laminatability]

A resin sheet (50 μm thick) was interposed between a circuit-formingsurface of a glass epoxy substrate FR-4 (MCL-E-67, manufactured byHitachi Chemical Co., Ltd.; thickness of copper foil: 12 μm, totalthickness: 1.2 mm) having a circuit with a height of 18 μm, a circuitwidth of 50 μm, and a circuit spacing of 50 μm and a glossy surface of acopper foil (BHY22BT, manufactured by Japan Energy Corporation), andheat and pressure were applied for one hour at a temperature of 180° C.and a pressure of 3 MPa to produce a laminate. The copper foil of theresulting laminate was chemically removed using an iron(III)chloride-hydrochloric acid solution. The exposed surface of the resinsheet was visually observed using an optical microscope (magnification:50 times) to check whether or not bubbles were included in the spacebetween the circuits.

Laminatability was evaluated according to the following criteria:

Satisfactory (◯): No inclusion of bubbles was observed in the spacebetween the circuits.

Unsatisfactory (x): Inclusion of bubbles was observed.

[Calculation of Volatile Component Content in Resin Sheet]

Using a thermogravimetric analyzer (TGA50, manufactured by ShimadzuCorporation), a resin sheet was placed in a sample container, andchanges in weight were observed under the conditions described below.The volatile component content was determined as the ratio of thedecrease in weight in the temperature range of 100° C. to 300° C. to theweight of the resin sheet before the change.

Measurement temperature range: 15° C. to 350° C.

Heating rate: 20° C./min

Measurement atmosphere: Nitrogen, flow rate 50 mL/min

Sample container: composed of aluminum

[Dielectric Characteristics]

Using a cavity resonator for complex permittivity measurement inperturbation method (trade name, manufactured by Kanto ElectronicsApplication and Development Inc.), the dielectric constant anddielectric loss tangent of a cured resin sheet were measured under thefollowing conditions:

Measurement frequency: 3 GHz, 5 GHz, and 10 GHz

Measurement temperature: 22° C. to 24° C.

Measurement humidity: 45% to 55%

Sample measured: Resin sheet left to stand for 24 hours at theabove-described measurement temperature and humidity

[Glass Transition Temperature]

Using a DMS-200 (manufactured by Seiko Instruments & Electronics Ltd.),the storage modulus (∈′) of a cured resin sheet was measured at ameasurement length (fixture gap) of 20 mm under the conditions describedbelow, and the inflection point of the storage modulus (∈′) wasdetermined as the glass transition temperature (° C.).

Measurement atmosphere: dry air atmosphere

Measurement temperature: 20° C. to 400° C.

Sample measured: Cured resin sheet strip having a width of 9 mm and alength of 40 mm

[Resistance to Soldering Heat]

A copper foil laminate having copper layers on both surfaces, which wasobtained in each example described below, was prepared and humiditycontrolling was performed under the conditions described below. Thecopper foil laminate was then dipped in a molten solder at 260° C. forone minute, and the copper foil on one side only was etched.Subsequently, the resin portion was visually checked. If no defects,such as bubbling and blistering were observed, the sample was consideredto be satisfactory.

Shape of sample: 15 mm×30 mm

Humidity control conditions: Left to stand for 24 hours at a temperatureof 22.5° C. to 23.5° C. and a humidity of 39.5% to 40.5%.

[Flame Retardance]

Evaluation was conducted according to the UL standard.

Synthesis Example 1 Polyimide Resin

Into a 2,000-mL glass flask charged with dimethylformamide (hereinafterreferred to as “DMF”), 0.95 equivalents of1,3-bis(3-aminophenoxy)benzene (hereinafter referred to as “APB”) and0.05 equivalents of 3,3′-dihydroxy-4,4′-diaminobiphenyl (manufactured byWakayama Seika Kogyo Co., Ltd.) were added and dissolved under stirringin a nitrogen atmosphere to prepare a DMF solution. Subsequently, afterthe flask was purged with nitrogen, the DMF solution was cooled in anice bath under stirring, and 1 equivalent of4,4′-(4,4′-isopropylidenediphenoxy)bisphthalic anhydride (hereinafterreferred to as “IPBP”) was added thereto. The resulting mixture wasstirred further for 3 hours to obtain a polyamic acid solution. Theamount of the DMF used was set so that the charge ratio of APB,3,3′-dihydroxy-4,4′-diaminobiphenyl, and IPBP monomers was 30% byweight.

The polyamic acid solution in an amount of 300 g was transferred to avat coated with a fluororesin, reduced pressure heating was performed ina vacuum oven for 3 hours at 200° C. and 5 mmHg (about 0.007 atmosphericpressure, about 5.65 hPa), and thereby a polyimide resin was obtained.

Synthesis Example 2 Synthesis of Phosphazene Compound as StartingMaterial

Into a 5-L flask equipped with a reflux condenser, a thermometer, anagitator, a phosphorus trichloride dropping funnel, and a chlorine gasblowing tube, 2.5 L of chlorobenzene, 182.5 g (3.4 mol) of ammoniumchloride, and 2.5 g of zinc chloride were charged to prepare a mixeddispersion liquid. The dispersion liquid was heated to 130° C., and425.5 g of phosphorus trichloride was dripped under refluxing at a rateof 9 g/min over 48 minutes. At the same time, 227 g of chlorine gas wasfed at a rate of 5 g/min over 46 minutes. After phosphorus trichlorideand chlorine gas were fed, reflux (131° C.) was further performed for150 minutes to complete the reaction. Subsequently, unreacted ammoniumchloride was removed by suction filtration. The filtrate was subjectedto a reduced pressure of 1.0 to 3.0 hPa, and chlorobenzene was distilledoff at 30° C. to 50° C. Thereby, 352 g of a reaction product wasobtained. The yield of the reaction product on the basis of phosphorustrichloride was 98.1%.

The resulting reaction product was redissolved in chlorobenzene, and amixture of hexachlorocyclotriphosphosphazene andoctachlorocyclotetraphosphazene (226 g, hexachlorocyclotriphosphazene:76%, octachlorocyclotetraphosphazene: 24%) was obtained byrecrystallization.

The chlorobenzene solution remaining after the recrystallization wasconcentrated, and 125 g of a mixture of cyclic chlorophosphazenecompounds (wherein m represents 3 to 15) was obtained. Furthermore, themixture of hexachlorocyclotriphosphosphazene andoctachlorocyclotetraphosphazene which was obtained first was subjectedto recrystallization three times using hexane, and thereby, 155 g ofhexachlorocyclotriphosphazene with a purity of 99.9% was obtained.

Synthesis Example 3 Synthesis of Phenoxyphosphazene Compound (D-1)

Into a 2-L four-necked flask equipped with a reflux condenser, athermometer, an agitator, and a dropping funnel, 58 g (0.5 unit mol,NPC12 being one unit) of hexachlorocyclotriphosphazene with a purity of99.9% and 100 mL of THF were charged to prepare a solution.Subsequently, a separately prepared THF solution of Na salt of4-methoxyphenol (4-methoxyphenol 68.3 g (0.55 mol), sodium 11.1 g (0.44g-atom), and THF 200 mL) was added dropwise to the THF solution ofhexachlorocyclotriphosphazene over one hour under stirring. Since thereaction was highly exothermic, the reaction was allowed to proceedwhile properly cooling so that the reaction temperature did not exceed30° C. After dropping was completed, stirring was continued for 6 hoursat 60° C. The residual chlorine content in the partially substitutedcompound obtained by this reaction was 15.78%, and the estimatedstructure was N3P3Cl3.36(OC6H4OCH3)2.63.

Subsequently, a separately prepared THF solution of a sodium phenolate(phenol 61.2 g (0.65 mol), sodium 13.8 g (0.6 g-atom), and THF 200 mL)was added dropwise to the reaction solution over one hour while coolingso that the reaction temperature was controlled to 30° C. or less.Subsequently, the reaction was carried out at room temperature for 5hours and at the reflux temperature. for 3 hours to complete thereaction. After the reaction was completed, the solvent, i.e., THF, wasremoved by distillation under reduced pressure, and then 500 mL oftoluene was added thereto to redissolve the product. Water (300 mL) wasfurther added to perform washing and liquid separation. The organiclayer was washed with a 5% by weight aqueous sodium hydroxide solutionand washed with a 2% by weight aqueous sodium hydroxide solution eachonce. Then, washing was performed with an (1+9) aqueous hydrochloricacid solution once, with a 5% by weight aqueous sodium hydrogencarbonateonce, and with water twice to neutralize the aqueous layer.

Subsequently, the organic layer was separated and dehydrated withanhydrous magnesium sulfate, and toluene was removed by distillation toobtain 122.6 g of a light yellow oily product (yield 95%). The residualchlorine content was 0.01% or less.

Into a 2-L four-necked flask, 116.2 g (0.45 unit mol) of the4-methoxyphenoxy and phenoxy groups mixed, substitutedcyclotriphosphazene obtained by the method described above and 583.6 g(5.05 mol) of pyridine hydrochloride were charged. The temperature wasgradually increased, and a reaction was carried out at 205° C. to 210°C. for one hour. After cooling to room temperature, 300 mL of water wasadded to dissolve the reaction product and the excess pyridinehydrochloride, and the reaction solution was controlled to pH6 to 7 witha 20% by weight aqueous sodium hydroxide solution.

Subsequently, extraction was performed four times using 500 mL of ethylacetate. Then, the extracts were combined, and washing was performedfour times with 500 mL of saturated aqueous sodium sulfate. The organiclayer was separated and dehydrated with anhydrous magnesium sulfate, andethyl acetate was removed by distillation under reduced pressure.Subsequently, the concentrate was dissolved in 200 mL of methanol, andthe resulting solution was poured into 1.5 L of water to precipitatecrystals. This process was repeated three times. The resulting crystalswere dried under reduced pressure to obtain 90.5 g of a yellow solid(yield 81.8%).

In the resulting compound, the residual chlorine content was 0.01% orless, and the hydroxyl group content was 6.1% (theoretical value 6.1%,structural formula N3P3(OPh)3.36(OC6H4OH)2.63, hydroxyl group equivalent279 g/eq).

First Embodiment Example 1

The polyimide resin (PI) prepared as described above, adicyclopentadiene-type epoxy resin (HP7200, epoxy value=277 g/eq,manufactured by Dainippon Ink and Chemicals, Inc.) as an epoxy resin(EP), 11 g of a naphthol/cresol copolymer-type phenol resin (NC30,hydroxyl value =126 g/eq, manufactured by Gunei Chemical Industry Co.,Ltd.) as a phenol resin (PH), and 2-ethyl-4-methylimidazole(manufactured by Shikoku Chemicals Co., Ltd.; 2E4MZ in Table 1) as acuring accelerator (CA), at a mixing ratio shown in Table 1, weredissolve in dioxolane to prepare a resin solution.

The resulting resin solution was flow-cast on a surface of a125-μm-thick PET film (trade name: Cerapeel HP, manufactured by ToyoMetallizing Co., Ltd.) serving as a support. The cast resin washeat-dried in a hot-air oven at 60° C., 80° C., 100° C., 120° C., and140° C. for three minutes each to produce a two-layer sheet having thePET film as a film base. From this two-layer sheet, the PET film wasremoved to obtain a one-layer resin sheet. The thickness of theresulting one-layer resin sheet (before thermal curing) was 50 μm. Theresin flowability, laminatability, and volatile component content of theresulting resin sheet (before thermal curing) were evaluated accordingto the evaluation methods described above. The results thereof are shownin Table 2.

Furthermore, the resin sheet was interposed between rolled copper foils(BHY-22B-T, manufactured by Japan Energy Corporation) having a thicknessof 18 μm such that the resin sheet came into contact with the roughenedsurfaces of the rolled copper foils. The resin sheet and the foils werethermally pressed for one hour at 180° C. and a pressure of 3 MPa toproduce a copper foil laminate (including the one-layer resin sheetsandwiched between the rolled copper foils). The copper foils wereremoved from the resulting copper foil laminate by etching to obtain acured resin sheet. The dielectric characteristics and the glasstransition temperature of the cured resin sheet were measured. Theresults thereof are shown in Table 3.

Examples 2 to 4

A resin sheet (before thermal curing) and a cured resin sheet obtainedby curing this resin sheet were produced as in Example 1 except that thepolyimide resin, the epoxy resin, the phenol resin, and the curingaccelerator shown in Table 1 were mixed at the ratio shown in Table 1.Note that, in Table 1, 157S65 (manufactured by Japan Epoxy Resin Co.,Ltd.) is a bisphenol A novolac-type epoxy resin, EXA4701 (manufacturedby Dainippon Ink and Chemicals, Inc.) is a naphthalene-type epoxy resin.Furthermore, PS6492 (manufactured by Gunei Chemical Industry Co., Ltd.)is a cresol/melamine copolymer-type phenol resin, and PSM4324(manufactured by Gunei Chemical Industry Co., Ltd.) is a phenolnovolac-type phenol resin.

The flowability, laminatability, and volatile component content of theresulting resin sheet were evaluated. The dielectric characteristics andthe glass transition temperature of the cured resin sheet wereevaluated. The results thereof are shown in Tables 2 and 3.

Comparative Examples 1 and 2

A resin sheet (before thermal curing) and a cured resin sheet obtainedby curing this resin sheet were produced as in Example 1 except that thepolyimide resin, the epoxy resin, the phenol resin, and the curingaccelerator were mixed at the ratio shown in Table 1. The flowability,laminatability, and volatile component content of the resulting resinsheet were evaluated. The dielectric characteristics and the glasstransition temperature of the cured resin sheet were evaluated. Theresults thereof are shown in Tables 2 and 3.

TABLE 1 Comparative Example Example 1 2 3 4 1 2 Polyimide resin (PI)Amount used (g) 65 30 50 50 20 70 Epoxy resin (EP) Type HP7200HH*¹157S65*² EXA4701*¹ HP7200HH*¹ Epoxy value 277 277 208 167 277 277 (g/eq)Amount used (g) 24 48 38 29 58 22 Number of moles of epoxy 0.087 0.1740.183 0.174 0.209 0.079 group (mol) Phenol resin (PH) Type*³ NC30 PS6492PSM4324 PSM4324 Phenol value 126 126 148 104 104 104 (g/eq) Amount used(g) 11 22 12 21 22 8 Number of moles of 0.087 0.174 0.081 0.202 0.2120.077 phenolic hydroxyl group (mol) Curing accelerator (CA) Type 2E4MZ2E4MZ Amount used (g) 0.24 0.48 0.04 0.3 0.6 0.2 Mixing ratio PI/(PH +EP)[mass] 1.85 0.43 1.00 1.00 0.25 2.33 PH/EP [mole] 1.00 1.00 0.44 1.161.01 0.97 *¹HP7200HH, EXA4701: manufactured by Dainippon Ink andChemicals, Inc. *²157S65: manufactured by Japan Epoxy Resin Co., Ltd.*³Phenol resin (NC30, PS6492, PSM4324): Gunei Chemical Industry Co.,Ltd.

TABLE 2 Complex Volatile component viscosity content (Pa · S)Laminatability (% by weight) Example 1 4.3 × 10³ ∘ 3.5 2 2.1 × 10³ ∘ 3.23 2.8 × 10³ ∘ 3.1 4 3.4 × 10³ ∘ 3.3 Comparative 1 1.0 × 10³ ∘ 2.8Example 2 2.0 × 10⁴ x 3.6

TABLE 3 Glass transition Dielectric characteristics temperature(dielectric constant/dielectric loss tangent) (° C.) Frequency: 3 GHzFrequency: 5 GHz Frequency: 10 GHz Example 1 152 2.9/0.011 2.8/0.0112.8/0.012 2 159 3.1/0.017 3.1/0.017 3.1/0.017 3 174 3.0/0.018 3.0/0.0183.0/0.019 4 149 3.1/0.018 3.1/0.019 3.1/0.020 Comparative 1 1613.3/0.024 3.2/0.024 3.2/0.027 Example 2 151 3.0/0.012 3.0/0.0122.9/0.013

As is obvious from the results described above, by producing a resinsheet using a thermosetting resin composition in which the mixing ratioby weight (A)/[(B)+(C)] is set at 0.4 to 2.0, the mixing ratio by weightbeing the ratio of the weight of a polyimide resin (A) to the totalweight of a phenol resin (B) and an epoxy resin (C), it is possible toachieve excellent flowability and laminatability and to obtain a curedresin sheet having excellent dielectric characteristics and the glasstransition temperature that can result in good heat resistance andplasticity.

Second Embodiment Example 5

A resin solution was prepared by dissolving 50 g of the solublepolyimide resin obtained in Synthesis Example 1, 25.0 g of2,2′-bis(4-phenylcyanate)propane (trade name: BADCY, manufactured byLonza Inc.), i.e., bisphenol A-based cyanate ester compound, as acyanate ester compound, and 25.0 g of phenoxyphosphazene compound(hydroxyl group equivalent=279 g/eq) obtained in Synthesis Example 2 indioxolane. The summary of the composition is shown in Table 4.

The resulting resin solution was flow-cast on a surface of a125-μm-thick PET film (trade name: Cerapeel HP, manufactured by ToyoMetallizing Co., Ltd.) serving as a support. The cast resin washeat-dried in a hot-air oven at 60° C., 80° C., 100° C., 120° C., and140° C. for three minutes each to produce a two-layer resin sheet havingthe PET film as a base. From this two-layer sheet, the PET film wasremoved to obtain a one-layer resin sheet. The thickness of theresulting one-layer resin sheet (before thermal curing) was 50 μm. Theresulting resin sheet was interposed between rolled copper foils (tradename: BHY-22B-T, manufactured by Japan Energy Corporation) having athickness of 18 μm such that the surfaces of the resin sheet were incontact with the roughened surfaces of the rolled copper foils. Theresin sheet and the foils were thermally pressed for one hour at 200° C.and a pressure of 3 MPa to produce a copper foil laminate (including theone-layer resin sheet sandwiched between the rolled copper foils).

Using the resulting copper foil laminate having copper foil layers atboth surfaces, resistance to soldering heat was evaluated.

The result thereof is shown in Table 5. Furthermore, the copper foils ofthe resulting copper foil laminate were removed by etching to obtain acured sheet. The dielectric characteristics, glass transitiontemperature, and flame retardance of the resulting cured sheet weremeasured. The results thereof are shown in Table 5.

Examples 6 to 11

A thermosetting resin composition was prepared as in Example 1 exceptthat the soluble polyimide resin, the phosphazene compound, the cyanateester compound, and the curing accelerator were mixed at a predeterminedratio shown in Table 4. As the cyanate ester compound, in Examples 6 and7, BADCY was used, and in Example 8, 4,4′-methylenebis(2,6-dimethylphenylcyanate) (trade name: Methylcy, manufactured by LonzaInc.) was used. In Example 9,2,2′-bis(4-phenylcyanate)-hexafluoropropane (trade name: fluorocy,manufactured by Lonza Inc.) was used, and in Example 6,oligo(3-methylene-1,5-phenylenecyanate) (trade name: PT-60, manufacturedby Lonza Inc.) was used.

Using the resulting thermosetting resin composition, a resin sheet(before thermal curing) and a cured resin sheet were obtained using thesame method conditions as those in Example 5. The resistance tosoldering heat, dielectric characteristics, glass transitiontemperature, and flame retardance of each of the resulting resin sheetswere measured. The results thereof are shown in Table 5.

Comparative Example 3

A resin solution was prepared by dissolving 50 g of the solublepolyimide resin obtained in Synthesis Example 1 and 50.0 g of2,2′-bis(4-phenylcyanate)propane (trade name: BADCY, manufactured byLonza Inc.), i.e., a bisphenol A-based cyanate ester compound, as acyanate ester compound, in dioxolane. The summary of the composition isshown in Table 1.

The resulting resin solution was flow-cast on a surface of a125-μm-thick PET film (trade name: Cerapeel HP, manufactured by ToyoMetallizing Co., Ltd.) serving as a support. The cast resin washeat-dried in a hot-air oven at 60° C., 80° C., 100° C., 120° C., and140° C. for three minutes each to produce a two-layer resin sheet havingthe PET film as a base.

The PET film was removed from the resin sheet to obtain a one-layerresin sheet. The thickness of the resulting one-layer resin sheet(before thermal curing) was 50 μm. The resulting resin sheet wasinterposed between rolled copper foils (trade name: BHY-22B-T,manufactured by Japan Energy Corporation) having a thickness of 18 μmsuch that the surfaces of the resin sheet were in contact with theroughened surfaces of the rolled copper foils. The resin sheet and thefoils were thermally pressed for one hour at 200° C. and a pressure of 3MPa to produce a copper foil laminate (including the one-layer resinsheet sandwiched between the rolled copper foils).

Using the resulting copper foil laminate having copper foil layers atboth surfaces, resistance to soldering heat was evaluated.

The result thereof is shown in Table 5. Furthermore, the copper foils ofthe resulting copper foil laminate were removed by etching to obtain acured sheet. The dielectric characteristics, glass transitiontemperature, and flame retardance of the resulting cured sheet weremeasured. The results thereof are shown in Table 5.

Comparative Example 4

A resin solution was prepared by dissolving 50 g of the solublepolyimide resin obtained in Synthesis Example 1, 35.0 g of2,2′-bis(4-phenylcyanate)propane (trade name: BADCY, manufactured byLonza Inc.), i.e., a bisphenol A-based cyanate ester compound, as acyanate ester compound, and 15.0 g of2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane (hereinafter referred to asTB-BPA, manufactured by Wako Pure Chemical Industries, Ltd.) indioxolane. The summary of the composition is shown in Table 4.

The resulting resin solution was flow-cast on a surface of a125-μm-thick PET film (trade name: Cerapeel HP, manufactured by ToyoMetallizing Co., Ltd.) serving as a support. The cast resin washeat-dried in a hot-air oven at 60° C., 80° C., 100° C., 120° C., and140° C. for three minutes each to produce a two-layer resin sheet havingthe PET film as a base.

The PET film was removed from the resin sheet to obtain a one-layerresin sheet. The thickness of the resulting one-layer resin sheet(before thermal curing) was 50 μm. The resulting resin sheet wasinterposed between rolled copper foils (trade name: BHY-22B-T,manufactured by Japan Energy Corporation) having a thickness of 18 μmsuch that the surfaces of the resin sheet were in contact with theroughened surfaces of the rolled copper foils. The resin sheet and thefoils were thermally pressed for one hour at 200° C. and a pressure of 3MPa to produce a copper foil laminate (including the one-layer resinsheet sandwiched between the rolled copper foils).

Using the resulting copper foil laminate having copper foil layers atboth surfaces, resistance to soldering heat was evaluated.

The result thereof is shown in Table 5. Furthermore, the copper foils ofthe resulting copper foil laminate were removed by etching to obtain acured sheet. The dielectric characteristics, glass transitiontemperature, and flame retardance of the resulting cured sheet weremeasured. The results thereof are shown in Table 5.

A resin composition was prepared as in Example 1 except that the solublepolyimide resin, the phosphazene compound, the cyanate ester compound,and the curing accelerator were mixed at a predetermined ratio shown inTable 1. Using the resulting resin composition, a resin sheet (beforethermal curing) and a cured resin sheet were obtained using the samemethod and conditions as those in Example 1. The resistance to solderingheat, dielectric characteristics, glass transition temperature, andflame retardance of each of the resulting resin sheets were measured.The results thereof are shown in Table 5.

TABLE 4 Comparative Example Example 5 6 7 8 9 10 11 3 4 Polyimide resin(PI) Amount used (g) 50 50 30 50 50 50 50 50 50 Cyanate ester compound(CY) Type I I I II III IV I I I Amount used (g) 25 42 35 25 25 25 20 5035 Phosphazene compound (P) Amount used (g) 25 8 35 25 25 25 50 — —Other component: Curing catalyst Type — V — — — — — V — Amount used (g)0.01 — 0.01 — TB-BPA Amount used (g) 15 Mixing ratio P/(PI + CY + P)0.25 0.08 0.35 0.25 0.25 0.25 0.42 0 0 I BADCY (trade name):2,2′-bis(4-phenylcyanate)propane II Methylcy (trade name):4,4′-methylenebis(2,6- dimethylphenylcyanate) III fluorocy (trade name):2,2′-bis(4-phenylcyanate)-hexafluoropropane IV PT-60 (trade name):oligo(3-methylen-1,5-phnylenecyanate) (I to IV each manufactured byLonza Inc.) V Cu(AA): copper(II) acetylacetonate

TABLE 5 Comparative Example Example 5 6 7 8 9 10 11 3 4 Dielectricconstant/ dielectric loss tangent  3 GHz 2.8/ 2.9/ 3.0/ 2.7/ 2.6/ 2.8/3.3/ 3.0/ 3.8/ 0.08 0.09 0.10 0.05 0.05 0.09 0.11 0.09 0.018  5 GHz 2.9/2.8/ 3.1/ 2.8/ 2.7/ 2.9/ 3.1/ 2.8/ 3.7/ 0.07 0.09 0.11 0.06 0.06 0.090.14 0.09 0.018 10 GHz 2.9/ 2.7/ 3.1/ 2.8/ 2.7/ 2.9/ 3.0/ 2.9/ 3.7/ 0.070.09 0.10 0.06 0.06 0.10 0.15 0.10 0.019 Glass transition 172 209 168168 163 197 128 215 147 temperature (° C.) Resistance to soldering heat260(° C.)/min PASS PASS PASS PASS PASS PASS Blistering PASS Blisteringoccurred occurred Flame retardance (UL) 94V-0 94V-0 94V-0 94V-0 94V-094V-0 94V-0 Burned 94V-0[Advantages of the Invention]

As described above, a thermosetting resin composition of the presentcomposition contains a polyimide resin, a phenol resin, and an epoxyresin as essential components, the epoxy resin and the phenol resinbeing mixed at a predetermined ratio with the polyimide resin.Furthermore, in the thermosetting resin composition of the presentinvention, the mixing ratio between the epoxy resin and the phenol resinis set at a predetermined value.

Therefore, it is possible to provide a thermosetting resin compositionexcellent in flowability required for embedding a circuit, adhesivenessto an adherend, such as a circuit board, processability andhandleability enabling bonding at low temperatures, and heat resistancewith respect to thermal expansion and thermal decomposition.Furthermore, it is possible to provide a thermosetting resin compositionin which a cured resin obtained by curing the thermosetting resincomposition has a much lower dielectric constant and a much lowerdielectric loss tangent in the GHz range compared with a conventionalresin composition including a polyimide resin and an epoxy resin, thushaving excellent dielectric characteristics.

Consequently, compared with the conventional resin composition, bondingat a lower temperature is enabled, and superior processability,handleability, heat resistance, and dielectric characteristics areshown. Thus, it is possible to provide a thermosetting resin compositionhaving various properties in a well-balanced manner, which isadvantageous.

Furthermore, a thermosetting resin composition of the present inventioncontains a polyimide resin (A), a phosphazene compound (D), and acyanate ester compound (E), and as the phosphazene compound (D), aphosphazene compound having a specific structure is used.

As a result, it is possible to sufficiently satisfy the requirements ofboth flame retardance and other physical properties, such as heatresistance, processability (including solvent solubility), anddielectric characteristics.

INDUSTRIAL APPLICABILITY

A thermosetting resin composition of the present composition contains apolyimide resin, a phenol resin, and an epoxy resin as essentialcomponents, the epoxy resin and the phenol resin being mixed at apredetermined ratio with the polyimide resin.

Furthermore, a thermosetting resin composition of the present inventioncontains a polyimide resin (A), a phosphazene compound (D), and acyanate ester compound (E), and as the phosphazene compound (D), aphosphazene compound having a specific structure is used.

These thermosetting resin compositions can be suitably used formultilayer bodies, such as circuit boards, e.g., flexible printedcircuit boards (FPCs) and build-up circuit boards, and as laminatingmaterials constituting such multilayer bodies. In particular, thethermosetting resin compositions can be suitably used for manufacturingprinted circuit boards that can sufficiently meet the requirement ofimproving information processing capability in electronic devices.Furthermore, for example, when the thermosetting resin composition ofthe present invention is formed into a varnish solution or the like, itis possible to produce a resin preparation useful as an adhesive, acoating material, an ink, or the like. Therefore, the present inventionis applicable not only in various resin industries and the chemicalindustry which manufacture thermosetting resin compositions, but also inthe resin processing industry which manufactures resin preparations,multilayer bodies, etc., the electronic part industry which manufacturescircuit boards, etc., and the electronic device industry.

1. A thermosetting resin composition comprising at least a polyimideresin component (A) containing at least one polyimide resin, a phenolresin component (B) containing at least one phenol resin, and an epoxyresin component (C) containing at least one epoxy resin, wherein themixing ratio by weight (A)/[(B)+(C)] is in a range of 0.4 to 2.0, themixing ratio by weight being the ratio of the weight of the polyimideresin component (A) to the total weight of the phenol resin component(B) and the epoxy resin component (C), wherein the phenol resincomponent (B) contains at least one phenol resin selected from the groupconsisting of compounds having structures represented by the formulae:

wherein a, b, c, and d, each represent an integer of 1 to
 10. 2. Athermosetting resin composition comprising at least a polyimide resincomponent (A) containing at least one polyimide resin, a phenol resincomponent (B) containing at least one phenol resin and an epoxy resincomponent (C) containing at least one epoxy resin, wherein the mixingratio by weight (A)/[(B)+(C)] is in a range of 0.4 to 2.0, the mixingratio by weight being the ratio of the weight of the polyimide resincomponent (A) to the total weight of the phenol resin component (B) andthe epoxy resin component (C), wherein the epoxy resin component (C)contains at least one epoxy resin selected from the group consisting ofcompounds having structures represented by the formulae:

wherein g, h, i, j, and k each represent an integer of 1 to
 10. 3. Athermosetting resin composition comprising at least a polyimide resin(A) containing at least one polyimide resin, a phosphazene compound (D)containing at least one phosphazene compound, and a cyanate estercompound (E) containing at least one cyanate ester compound, wherein thephosphazene compound (D) comprises a phenolic hydroxyl group-containingphenoxyphosphazene compound (D-1) and/or a crosslinkedphenoxyphosphazene compound (D-2) prepared by crosslinking thephenoxyphosphazene compound (D-1), the crosslinked phenoxyphosphazenecompound (D-2) having at least one phenolic hydroxyl group.
 4. Thethermosetting resin composition according to claim 3, wherein the mixingratio by weight (D)/[(A)+(D)+(E)] is in a range of 0.01 to 0.4, themixing ratio by weight being the ratio of the weight of the phosphazenecompound (D) to the total weight of the polyimide resin (A), thephosphazene compound (D), and the cyanate ester compound (E).
 5. Thethermosetting resin composition according to claims 3 or 4, wherein thephenoxyphosphazene compound (D-1) comprises at least a cyclicphenoxyphosphazene compound (D-11) represented by general formula (2):

wherein m represents an integer of 3 to 25; R¹ and R² each represent aphenyl group or a hydroxyphenyl group; and at least one hydroxyphenylgroup is contained per molecule and/or a linear phenoxyphosphazenecompound (D-12) represented by general formula (3):

wherein n represents an integer of 3 to 10,000; R³ and R⁴ each representa phenyl group or a hydroxyphenyl group; at least one hydroxyphenylgroup is contained per molecule; R⁵ represents —N═P(OC₆H₅)₃,—N═P(OC₆H₅)₂(OC₆H₄OH), —N═P(OC₆H₅)(OC₆H₄OH)₂, —N═P(OC₆H₄OH)₃,—N═P(O)OC₆H₅, or —N═P(O)(OC₆H₄OH); and R⁶ represents —P(OC₆H₅)₄,—P(OC₆H₅)₃(OC ₆H₄OH), —P(OC₆H₅)₂(OC₆H₄OH)₂, —P(OC₆H₅)(OC₆H₄OH)₃,—P(OC₆H₄OH)₄, —P(O)(OC₆H₅)₂, —P(O)(OC₆H₅)(OC₆H₄OH), or —P(O)(OC₆H₄OH)₂.6. The thermosetting resin composition according to claim 5, wherein thecrosslinked phenoxyphosphazene compound (D-2) is prepared bycrosslinking the phenoxyphosphazene compound (D-1) with aphenylene-based crosslinking group containing at least any one of ano-phenylene group, an m-phenylene group, a p-phenylene group, and abisphenylene group represented by general formula (4):

wherein R⁷ represents —C(CH₃)₂—, —SO₂—, —S—, or —O—; and p represents 0or
 1. 7. The thermosetting resin composition according to claim 6,wherein the crosslinked phenoxyphosphazene compound (D-2) is aphenylene-based crosslinked phenoxyphosphazene compound (D-21) having atleast one phenolic hydroxyl group, in which the cyclicphenoxyphosphazene compound (D-11) and/or the linear phenoxyphosphazenecompound (D-12) are used as the phenoxyphosphazene compound, and thephenylene-based crosslinking group lies between two oxygen atoms of thephenoxyphosphazene compound (D-1), the phenyl group and thehydroxyphenyl group being separated from the oxygen atoms, and thecontent of the phenyl group and the hydroxyphenyl group in thecrosslinked phenoxyphosphazene compound is in a range of 50% to 99.9%based on the total number of phenyl groups and hydroxyphenyl groupscontained in the phenoxyphosphazene compound.
 8. The thermosetting resincomposition according to claim 7, wherein the polyimide resin (A)contains a soluble polyimide resin.
 9. The thermosetting resincomposition according to claim 8, wherein the polyimide resin (A)dissolves in an amount of 1% by weight or more in at least one organicsolvent selected from the group consisting of dioxolane, dioxane,tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, andN-methyl-2-pyrrolidone in a temperature range of 15° C. to 100° C. 10.The thermosetting resin composition according to claim 9, wherein thepolyimide resin (A) contains at least one component for impartingorganic solvent solubility which is selected from the group consistingof an aliphatic compound component, an alicyclic compound component, anda bisphenol compound-alkylene oxide adduct component, so as to exhibitsolubility in a mixed solvent containing a low-boiling organic solvent.11. The thermosetting resin composition according to claim 10, whereinthe polyimide resin (A) is produced by reacting an acid dianhydridecomponent with a diamine component or an isocyanate component, and theacid dianhydride component contains at least an acid dianhydriderepresented by general formula (1):

wherein V represents a direct bond, —O—, —O-T-O—, —O—CO-T-CO—O—,—(C═O)—,—C(CF₃)₂—, or —C(CH₃)₂—, T representing a divalent organic group. 12.The thermosetting resin composition according to claim 11, wherein thepolyimide resin (A) is produced by reacting an acid dianhydridecomponent with a diamine component or an isocyanate component, and thediamine component or the isocyanate component contains at least any oneof a siloxane diamine, a diamine containing a hydroxyl group and/or acarboxyl group, a diamine having amino groups at the meta positions, adiamine having amino groups at the ortho positions, an isocyanate havingan amino group at the meta position, and an isocyanate having an aminogroup at the ortho position.
 13. The thermosetting resin compositionaccording to claim 12, wherein the cyanate ester compound (E) includesat least one compound selected from the group consisting of compoundsrepresented by the group of general formulae (1):

wherein r represents 0 to
 4. 14. A circuit board comprising a layerhaving a dielectric constant of 3.3 or less and a dielectric losstangent of 0.020 or less in a range of in a frequency range of 1 to 10GHz and being formed on wiring boards or circuits, wherein the layer isobtained by curing a thermosetting resin composition comprising at leasta polyimide resin component (A) containing at least one polyimide resin,a phenol resin component (B) containing at least one phenol resin, andan epoxy resin component (C) containing at least one epoxy resin,wherein the mixing ratio by weight (A)/[(B)+(C)] is in a range of 0.4 to2.0, the mixing ratio by weight being the ratio of the weight of thepolyimide resin component (A) to the total weight of the phenol resincomponent (B) and the epoxy resin component (C), wherein the phenolresin component (B) contains at least one phenol resin selected from thegroup consisting of compounds having structures represented by theformulae:

wherein a, b, c, d, and e each represent an integer of 1 to
 10. 15. Acircuit board comprising a layer having a dielectric constant of 3.3 orless and a dielectric loss tangent of 0.020 or less in a frequency rangeof 1 to 10 GHz and being formed on wiring boards or circuits, whereinthe layer is obtained by curing a thermosetting resin compositioncomprising at least a polyimide resin (A) containing at least onepolyimide resin, a phosphazene compound (D) containing at least onephosphazene compound, and a cyanate ester compound (E) containing atleast one cyanate ester compound, wherein the phosphazene compound (D)comprises a phenolic hydroxyl group-containing phenoxyphosphazenecompound (D-1) and/or a crosslinked phenoxyphosphazene compound (D-2)prepared by crosslinking the phenoxyphosphazene compound (D-1), thecrosslinked phenoxyphosphazene compound (D-2) having at least onephenolic hydroxyl group.
 16. The circuit board according to claim 15,wherein the mixing ratio by weight (D)/[(A)+(D)+(E)] is in a range of0.01 to 0.4, the mixing ratio by weight being the ratio of the weight ofthe phosphazene compound (D) to the total weight of the polyimide resin(A), the phosphazene compound (D), and the cyanate ester compound (E).17. The circuit board according to claims 15 or 16, wherein thephenoxyphosphazene compound (D-1) comprises at least a cyclicphenoxyphosphazene compound (D-11) represented by general formula (2):

wherein m represents an integer of 3 to 25; R¹ and R² each represent aphenyl group or a hydroxyphenyl group; and at least one hydroxyphenylgroup is contained per molecule and/or a linear phenoxyphosphazenecompound (D-12) represented by general formula (3):

wherein n represents an integer of 3 to 10,000; R³ and R⁴ each representa phenyl group or a hydroxyphenyl group; at least one hydroxyphenylgroup is contained per molecule; R⁵ represents —N═P(OC₆H₅)₃,—N═P(OC₆H₅)₂(OC₆H₄OH), —N═P(OC₆H₅)(OC₆H₄OH)₂, —N═P(OC₆H₄OH)₃,—N═P(O)OC₆H₅, or —N═P(O)(OC₆H₄OH); and R⁶ represents —P(OC₆H₅)₄,—P(OC₆H₅)₃(OC₆H₄OH), —P(OC₆H₅)₂(OC₆H₄OH)₂, —P(OC₆H₅)(OC₆H₄OH)₃,—P(OC₆H₄OH)₄, —P(O)(OC₆H₅)₂, —P(O)(OC₆H₅)(OC₆H₄OH), or —P(O)(OC₆H₄OH)₂.18. The circuit board according to claim 17, wherein the crosslinkedphenoxyphosphazene compound (D-2) is prepared by crosslinking thephenoxyphosphazene compound (D-1) with a phenylene-based crosslinkinggroup containing at least any one of an o-phenylene group, anm-phenylene group, a p-phenylene group, and a bisphenylene grouprepresented by general formula (4):

wherein R⁷ represents —C(CH₃)₂—, —SO₂—, —S—, or —O—; and p represents 0or
 1. 19. The circuit board according to claim 18, wherein thecrosslinked phenoxyphosphazene compound (D-2) is a phenylene-basedcrosslinked phenoxyphosphazene compound (D-21) having at least onephenolic hydroxyl group, in which the cyclic phenoxyphosphazene compound(D-11) and/or the linear phenoxyphosphazene compound (D-12) are used asthe phenoxyphosphazene compound, and the phenylene-based crosslinkinggroup lies between two oxygen atoms of the phenoxyphosphazene compound(D-1), the phenyl group and the hydroxyphenyl group being separated fromthe oxygen atoms, and the content of the phenyl group and thehydroxyphenyl group in the crosslinked phenoxyphosphazene compound is ina range of 50% to 99.9% based on the total number of phenyl groups andhydroxyphenyl groups contained in the phenoxyphosphazene compound. 20.The circuit board according to claim 19, wherein the polyimide resin (A)contains a soluble polyimide resin.
 21. The circuit board according toclaim 20, wherein the polyimide resin (A) dissolves in an amount of 1%by weight or more in at least one organic solvent selected from thegroup consisting of dioxolane, dioxane, tetrahydrofuran,N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidonein a temperature range of 15° C. to 100° C.
 22. The circuit boardaccording to claim 21, wherein the polyimide resin (A) contains at leastone component for imparting organic solvent solubility which is selectedfrom the group consisting of an aliphatic compound component, analicyclic compound component, and a bisphenol compound-alkylene oxideadduct component, so as to exhibit solubility in a mixed solventcontaining a low-boiling organic solvent.
 23. The circuit boardaccording to claim 22, wherein the polyimide resin (A) is produced byreacting an acid dianhydride component with a diamine component or anisocyanate component, and the acid dianhydride component contains atleast an acid dianhydride represented by general formula (1):

wherein V represents a direct bond, —O—, —O-T-O—, —O—CO-T-CO—O—,—(C═O)—, —C(CF₃)₂—, or —C(CH₃₎ ₂—, T representing a divalent organicgroup.
 24. The circuit board according to claim 23, wherein thepolyimide resin (A) is produced by reacting an acid dianhydridecomponent with a diamine component or an isocyanate component, and thediamine component or the isocyanate component contains at least any oneof a siloxane diamine, a diamine containing a hydroxyl group and/or acarboxyl group, a diamine having amino groups at the meta positions, adiamine having amino groups at the ortho positions, an isocyanate havingan amino group at the mets position, and an isocyanate having an aminogroup at the ortho position.
 25. The circuit board according to claim24, wherein the cyanate ester compound (E) includes at least onecompound selected from the group consisting of compounds represented bythe group of general formulae (1):

wherein r represents 0 to 4.